diff --git a/docs/chat.md b/docs/chat.md
index 4438c17360f..22064c73e8d 100644
--- a/docs/chat.md
+++ b/docs/chat.md
@@ -40,6 +40,7 @@ Base endpoint is: `/ocs/v2.php/apps/spreed/api/v1`
         `actorDisplayName` | string | Display name of the message author
         `timestamp` | int | Timestamp in seconds and UTC time zone
         `systemMessage` | string | empty for normal chat message or the type of the system message (untranslated)
+        `messageType` | string | Currently known types are `comment`, `system` and `command`
         `message` | string | Message string with placeholders (see [Rich Object String](https://github.com/nextcloud/server/issues/1706))
         `messageParameters` | array | Message parameters for `message` (see [Rich Object String](https://github.com/nextcloud/server/issues/1706))
 
@@ -53,6 +54,7 @@ Base endpoint is: `/ocs/v2.php/apps/spreed/api/v1`
     ------|------|------------
     `message` | string | The message the user wants to say
     `actorDisplayName` | string | Guest display name (ignored for logged in users)
+    `replyTo` | int | The message ID this message is a reply to (only allowed for messages from the same conversation and when the message type is not `system` or `command`)
 
 * Response:
     - Header:
diff --git a/js/models/chatmessage.js b/js/models/chatmessage.js
index dd27de33cf2..b435642d728 100644
--- a/js/models/chatmessage.js
+++ b/js/models/chatmessage.js
@@ -49,7 +49,8 @@
 			actorDisplayName: '',
 			timestamp: 0,
 			message: '',
-			messageParameters: []
+			messageParameters: [],
+			replyTo: 0
 		},
 
 		url: function() {
diff --git a/lib/Chat/ChatManager.php b/lib/Chat/ChatManager.php
index 11a101f465b..36550ef4a9d 100644
--- a/lib/Chat/ChatManager.php
+++ b/lib/Chat/ChatManager.php
@@ -138,10 +138,11 @@ public function addChangelogMessage(Room $chat, string $message): IComment {
 	 * @param string $actorType
 	 * @param string $actorId
 	 * @param string $message
+	 * @param IComment|null $replyTo
 	 * @param \DateTime $creationDateTime
 	 * @return IComment
 	 */
-	public function sendMessage(Room $chat, Participant $participant, string $actorType, string $actorId, string $message, \DateTime $creationDateTime): IComment {
+	public function sendMessage(Room $chat, Participant $participant, string $actorType, string $actorId, string $message, \DateTime $creationDateTime, ?IComment $replyTo): IComment {
 		$comment = $this->commentsManager->create($actorType, $actorId, 'chat', (string) $chat->getId());
 		$comment->setMessage($message, self::MAX_CHAT_LENGTH);
 		$comment->setCreationDateTime($creationDateTime);
@@ -149,6 +150,10 @@ public function sendMessage(Room $chat, Participant $participant, string $actorT
 		// comment
 		$comment->setVerb('comment');
 
+		if ($replyTo instanceof IComment) {
+			$comment->setParentId($replyTo->getId());
+		}
+
 		$this->dispatcher->dispatch(self::class . '::preSendMessage', new GenericEvent($chat, [
 			'comment' => $comment,
 			'room' => $chat,
@@ -161,13 +166,18 @@ public function sendMessage(Room $chat, Participant $participant, string $actorT
 			// Update last_message
 			$chat->setLastMessage($comment);
 
-			$mentionedUsers = $this->notifier->notifyMentionedUsers($chat, $comment);
-			if (!empty($mentionedUsers)) {
-				$chat->markUsersAsMentioned($mentionedUsers, (int) $comment->getId());
+			$alreadyNotifiedUsers = [];
+			if ($replyTo instanceof IComment) {
+				$alreadyNotifiedUsers = $this->notifier->notifyReplyToAuthor($chat, $comment, $replyTo);
+			}
+
+			$alreadyNotifiedUsers = $this->notifier->notifyMentionedUsers($chat, $comment, $alreadyNotifiedUsers);
+			if (!empty($alreadyNotifiedUsers)) {
+				$chat->markUsersAsMentioned($alreadyNotifiedUsers, (int) $comment->getId());
 			}
 
 			// User was not mentioned, send a normal notification
-			$this->notifier->notifyOtherParticipant($chat, $comment, $mentionedUsers);
+			$this->notifier->notifyOtherParticipant($chat, $comment, $alreadyNotifiedUsers);
 
 			$this->dispatcher->dispatch(self::class . '::sendMessage', new GenericEvent($chat, [
 				'comment' => $comment,
@@ -180,6 +190,22 @@ public function sendMessage(Room $chat, Participant $participant, string $actorT
 		return $comment;
 	}
 
+	/**
+	 * @param Room $chat
+	 * @param string $parentId
+	 * @return IComment
+	 * @throws NotFoundException
+	 */
+	public function getParentComment(Room $chat, string $parentId): IComment {
+		$comment = $this->commentsManager->get($parentId);
+
+		if ($comment->getObjectType() !== 'chat' || $comment->getObjectId() !== (string) $chat->getId()) {
+			throw new NotFoundException('Parent not found in the right context');
+		}
+
+		return $comment;
+	}
+
 	public function getLastReadMessageFromLegacy(Room $chat, IUser $user): int {
 		$marker = $this->commentsManager->getReadMark('chat', $chat->getId(), $user);
 		if ($marker === null) {
diff --git a/lib/Chat/Notifier.php b/lib/Chat/Notifier.php
index 4f44d034b41..8b744bee0f9 100644
--- a/lib/Chat/Notifier.php
+++ b/lib/Chat/Notifier.php
@@ -76,9 +76,10 @@ public function __construct(INotificationManager $notificationManager,
 	 *
 	 * @param Room $chat
 	 * @param IComment $comment
+	 * @param string[] $alreadyNotifiedUsers
 	 * @return string[] Users that were mentioned
 	 */
-	public function notifyMentionedUsers(Room $chat, IComment $comment): array {
+	public function notifyMentionedUsers(Room $chat, IComment $comment, array $alreadyNotifiedUsers): array {
 		$mentionedUserIds = $this->getMentionedUserIds($comment);
 		if (empty($mentionedUserIds)) {
 			return [];
@@ -92,13 +93,48 @@ public function notifyMentionedUsers(Room $chat, IComment $comment): array {
 
 		$notification = $this->createNotification($chat, $comment, 'mention');
 		foreach ($mentionedUserIds as $mentionedUserId) {
+			if (in_array($mentionedUserId, $alreadyNotifiedUsers, true)) {
+				continue;
+			}
+
 			if ($this->shouldUserBeNotified($mentionedUserId, $comment)) {
 				$notification->setUser($mentionedUserId);
 				$this->notificationManager->notify($notification);
+				$alreadyNotifiedUsers[] = $mentionedUserId;
 			}
 		}
 
-		return $mentionedUserIds;
+		return $alreadyNotifiedUsers;
+	}
+
+	/**
+	 * Notifies the author that wrote the comment which was replied to
+	 *
+	 * The comment must be a chat message comment. That is, its "objectId" must
+	 * be the room ID.
+	 *
+	 * The author of the message is notified only if he is still able to participate in the room
+	 *
+	 * @param Room $chat
+	 * @param IComment $comment
+	 * @param IComment $replyTo
+	 * @return string[] Users that were mentioned
+	 */
+	public function notifyReplyToAuthor(Room $chat, IComment $comment, IComment $replyTo): array {
+		if ($replyTo->getActorType() !== 'users') {
+			// No reply notification when the replyTo-author was not a user
+			return [];
+		}
+
+		if (!$this->shouldUserBeNotified($replyTo->getActorId(), $comment)) {
+			return [];
+		}
+
+		$notification = $this->createNotification($chat, $comment, 'reply');
+		$notification->setUser($replyTo->getActorId());
+		$this->notificationManager->notify($notification);
+
+		return [$replyTo->getActorId()];
 	}
 
 	/**
@@ -112,9 +148,9 @@ public function notifyMentionedUsers(Room $chat, IComment $comment): array {
 	 *
 	 * @param Room $chat
 	 * @param IComment $comment
-	 * @param string[] $mentionedUsers
+	 * @param string[] $alreadyNotifiedUsers
 	 */
-	public function notifyOtherParticipant(Room $chat, IComment $comment, array $mentionedUsers): void {
+	public function notifyOtherParticipant(Room $chat, IComment $comment, array $alreadyNotifiedUsers): void {
 		$participants = $chat->getParticipantsByNotificationLevel(Participant::NOTIFY_ALWAYS);
 
 		$notification = $this->createNotification($chat, $comment, 'chat');
@@ -128,7 +164,7 @@ public function notifyOtherParticipant(Room $chat, IComment $comment, array $men
 				continue;
 			}
 
-			if (\in_array($participant->getUser(), $mentionedUsers, true)) {
+			if (\in_array($participant->getUser(), $alreadyNotifiedUsers, true)) {
 				continue;
 			}
 
@@ -154,7 +190,7 @@ public function notifyOtherParticipant(Room $chat, IComment $comment, array $men
 					continue;
 				}
 
-				if (\in_array($participant->getUser(), $mentionedUsers, true)) {
+				if (\in_array($participant->getUser(), $alreadyNotifiedUsers, true)) {
 					continue;
 				}
 
diff --git a/lib/Chat/Parser/SystemMessage.php b/lib/Chat/Parser/SystemMessage.php
index 2fac2964e30..57ba2c8ec27 100644
--- a/lib/Chat/Parser/SystemMessage.php
+++ b/lib/Chat/Parser/SystemMessage.php
@@ -235,8 +235,7 @@ public function parseMessage(Message $chatMessage): void {
 			throw new \OutOfBoundsException('Unknown subject');
 		}
 
-		$comment->setMessage($message, ChatManager::MAX_CHAT_LENGTH);
-		$chatMessage->setMessage($parsedMessage, $parsedParameters);
+		$chatMessage->setMessage($parsedMessage, $parsedParameters, $message);
 	}
 
 	/**
diff --git a/lib/Controller/ChatController.php b/lib/Controller/ChatController.php
index 155b0528f34..293b5c9a065 100644
--- a/lib/Controller/ChatController.php
+++ b/lib/Controller/ChatController.php
@@ -28,6 +28,7 @@
 use OCA\Spreed\Chat\ChatManager;
 use OCA\Spreed\Chat\MessageParser;
 use OCA\Spreed\GuestManager;
+use OCA\Spreed\Model\Message;
 use OCA\Spreed\Room;
 use OCA\Spreed\TalkSession;
 use OCP\AppFramework\Http;
@@ -37,6 +38,7 @@
 use OCP\Collaboration\Collaborators\ISearchResult;
 use OCP\Comments\IComment;
 use OCP\Comments\MessageTooLongException;
+use OCP\Comments\NotFoundException;
 use OCP\IL10N;
 use OCP\IRequest;
 use OCP\IUserManager;
@@ -118,11 +120,12 @@ public function __construct(string $appName,
 	 *
 	 * @param string $message the message to send
 	 * @param string $actorDisplayName for guests
+	 * @param int $replyTo Parent id which this message is a reply to
 	 * @return DataResponse the status code is "201 Created" if successful, and
 	 *         "404 Not found" if the room or session for a guest user was not
 	 *         found".
 	 */
-	public function sendMessage(string $message, string $actorDisplayName = ''): DataResponse {
+	public function sendMessage(string $message, string $actorDisplayName = '', int $replyTo = 0): DataResponse {
 
 		if ($this->userId === null) {
 			$actorType = 'guests';
@@ -146,11 +149,27 @@ public function sendMessage(string $message, string $actorDisplayName = ''): Dat
 			return new DataResponse([], Http::STATUS_NOT_FOUND);
 		}
 
+		$parent = $parentMessage = null;
+		if ($replyTo !== 0) {
+			try {
+				$parent = $this->chatManager->getParentComment($this->room, (string) $replyTo);
+			} catch (NotFoundException $e) {
+				// Someone is trying to reply cross-rooms or to a non-existing message
+				return new DataResponse([], Http::STATUS_BAD_REQUEST);
+			}
+
+			$parentMessage = $this->messageParser->createMessage($this->room, $this->participant, $parent, $this->l);
+			$this->messageParser->parseMessage($parentMessage);
+			if ($parentMessage->getMessageType() === 'system' || $parentMessage->getMessageType() === 'command') {
+				return new DataResponse([], Http::STATUS_BAD_REQUEST);
+			}
+		}
+
 		$this->room->ensureOneToOneRoomIsFilled();
 		$creationDateTime = $this->timeFactory->getDateTime('now', new \DateTimeZone('UTC'));
 
 		try {
-			$comment = $this->chatManager->sendMessage($this->room, $this->participant, $actorType, $actorId, $message, $creationDateTime);
+			$comment = $this->chatManager->sendMessage($this->room, $this->participant, $actorType, $actorId, $message, $creationDateTime, $parent);
 		} catch (MessageTooLongException $e) {
 			return new DataResponse([], Http::STATUS_REQUEST_ENTITY_TOO_LARGE);
 		} catch (\Exception $e) {
@@ -164,17 +183,11 @@ public function sendMessage(string $message, string $actorDisplayName = ''): Dat
 			return new DataResponse([], Http::STATUS_CREATED);
 		}
 
-		return new DataResponse([
-			'id' => (int) $comment->getId(),
-			'token' => $this->room->getToken(),
-			'actorType' => $chatMessage->getActorType(),
-			'actorId' => $chatMessage->getActorId(),
-			'actorDisplayName' => $chatMessage->getActorDisplayName(),
-			'timestamp' => $comment->getCreationDateTime()->getTimestamp(),
-			'message' => $chatMessage->getMessage(),
-			'messageParameters' => $chatMessage->getMessageParameters(),
-			'systemMessage' => $chatMessage->getMessageType() === 'system' ? $comment->getMessage() : '',
-		], Http::STATUS_CREATED);
+		$data = $this->messageToData($chatMessage);
+		if ($parentMessage instanceof Message) {
+			$data['parent'] = $this->messageToData($parentMessage);
+		}
+		return new DataResponse($data, Http::STATUS_CREATED);
 	}
 
 	/**
@@ -241,28 +254,76 @@ public function receiveMessages(int $lookIntoFuture, int $limit = 100, int $last
 			return new DataResponse([], Http::STATUS_NOT_MODIFIED);
 		}
 
-		$messages = [];
+		$i = 0;
+		$messages = $commentIdToIndex = $parentIds = [];
 		foreach ($comments as $comment) {
+			$id = (int) $comment->getId();
 			$message = $this->messageParser->createMessage($this->room, $this->participant, $comment, $this->l);
 			$this->messageParser->parseMessage($message);
 
 			if (!$message->getVisibility()) {
+				$commentIdToIndex[$id] = null;
 				continue;
 			}
 
-			$messages[] = [
-				'id' => (int) $comment->getId(),
-				'token' => $this->room->getToken(),
-				'actorType' => $message->getActorType(),
-				'actorId' => $message->getActorId(),
-				'actorDisplayName' => $message->getActorDisplayName(),
-				'timestamp' => $comment->getCreationDateTime()->getTimestamp(),
-				'message' => $message->getMessage(),
-				'messageParameters' => $message->getMessageParameters(),
-				'systemMessage' => $message->getMessageType() === 'system' ? $comment->getMessage() : '',
-			];
+			if ($comment->getParentId() !== '0') {
+				$parentIds[$id] = $comment->getParentId();
+			}
+
+			$messages[] = $this->messageToData($message);
+			$commentIdToIndex[$id] = $i;
+			$i++;
 		}
 
+		/**
+		 * Set the parent for reply-messages
+		 */
+		$loadedParents = [];
+		foreach ($parentIds as $commentId => $parentId) {
+			$commentKey = $commentIdToIndex[$commentId];
+
+			// Parent is already parsed in the message list
+			if (!empty($commentIdToIndex[$parentId])) {
+				$parentKey = $commentIdToIndex[$parentId];
+				$messages[$commentKey]['parent'] = $messages[$parentKey];
+
+				// We don't show nested parents…
+				unset($messages[$commentKey]['parent']['parent']);
+				continue;
+			}
+
+			// Parent was already loaded manually for another comment
+			if (!empty($loadedParents[$parentId])) {
+				$messages[$commentKey]['parent'] = $loadedParents[$parentId];
+				continue;
+			}
+
+			// Parent was not skipped due to visibility, so we need to manually grab it.
+			if (!isset($commentIdToIndex[$parentId])) {
+				try {
+					$comment = $this->chatManager->getParentComment($this->room, $parentId);
+					$message = $this->messageParser->createMessage($this->room, $this->participant, $comment, $this->l);
+					$this->messageParser->parseMessage($message);
+
+					if ($message->getVisibility()) {
+						$loadedParents[$parentId] = $this->messageToData($message);
+						$messages[$commentKey]['parent'] = $loadedParents[$parentId];
+					} else {
+						$loadedParents[$parentId] = [
+							'id' => $parentId,
+							'deleted' => true,
+						];
+					}
+				} catch (NotFoundException $e) {
+				}
+			}
+
+			// Message is not visible to the user
+			$messages[$commentKey]['parent'] = [
+				'id' => $parentId,
+				'deleted' => true,
+			];
+		}
 
 		$response = new DataResponse($messages, Http::STATUS_OK);
 
@@ -277,6 +338,21 @@ public function receiveMessages(int $lookIntoFuture, int $limit = 100, int $last
 		return $response;
 	}
 
+	protected function messageToData(Message $message): array {
+		return [
+			'id' => (int) $message->getComment()->getId(),
+			'token' => $message->getRoom()->getToken(),
+			'actorType' => $message->getActorType(),
+			'actorId' => $message->getActorId(),
+			'actorDisplayName' => $message->getActorDisplayName(),
+			'timestamp' => $message->getComment()->getCreationDateTime()->getTimestamp(),
+			'message' => $message->getMessage(),
+			'messageParameters' => $message->getMessageParameters(),
+			'systemMessage' => $message->getMessageType() === 'system' ? $message->getMessageRaw() : '',
+			'messageType' => $message->getMessageType(),
+		];
+	}
+
 	/**
 	 * @NoAdminRequired
 	 * @RequireParticipant
diff --git a/lib/Controller/RoomController.php b/lib/Controller/RoomController.php
index 5018ae37e86..8277e26009e 100644
--- a/lib/Controller/RoomController.php
+++ b/lib/Controller/RoomController.php
@@ -327,7 +327,8 @@ protected function formatLastMessage(Room $room, Participant $participant, IComm
 			'timestamp' => $lastMessage->getCreationDateTime()->getTimestamp(),
 			'message' => $message->getMessage(),
 			'messageParameters' => $message->getMessageParameters(),
-			'systemMessage' => $message->getMessageType() === 'system' ? $lastMessage->getMessage() : '',
+			'systemMessage' => $message->getMessageType() === 'system' ? $message->getMessageRaw() : '',
+			'messageType' => $message->getMessageType(),
 		];
 	}
 
diff --git a/lib/Model/Message.php b/lib/Model/Message.php
index acb3848d9e9..a7e1f3ea571 100644
--- a/lib/Model/Message.php
+++ b/lib/Model/Message.php
@@ -52,6 +52,9 @@ class Message {
 	/** @var string */
 	protected $message = '';
 
+	/** @var string */
+	protected $rawMessage = '';
+
 	/** @var array */
 	protected $parameters = [];
 
@@ -106,9 +109,10 @@ public function getVisibility(): bool {
 		return $this->visible;
 	}
 
-	public function setMessage(string $message, array $parameters): void {
+	public function setMessage(string $message, array $parameters, string $rawMessage = ''): void {
 		$this->message = $message;
 		$this->parameters = $parameters;
+		$this->rawMessage = $rawMessage;
 	}
 
 	public function getMessage(): string {
@@ -119,6 +123,10 @@ public function getMessageParameters(): array {
 		return $this->parameters;
 	}
 
+	public function getMessageRaw(): string {
+		return $this->rawMessage;
+	}
+
 	public function setMessageType(string $type): void {
 		$this->type = $type;
 	}
diff --git a/lib/Notification/Notifier.php b/lib/Notification/Notifier.php
index 3c11cecab10..0b54a40af86 100644
--- a/lib/Notification/Notifier.php
+++ b/lib/Notification/Notifier.php
@@ -165,7 +165,7 @@ public function prepare(INotification $notification, string $languageCode): INot
 			}
 			return $this->parseCall($notification, $room, $l);
 		}
-		if ($subject === 'mention' || $subject === 'chat') {
+		if ($subject === 'reply' || $subject === 'mention' || $subject === 'chat') {
 			return $this->parseChatMessage($notification, $room, $participant, $l);
 		}
 
@@ -251,25 +251,31 @@ protected function parseChatMessage(INotification $notification, Room $room, Par
 		if ($notification->getSubject() === 'chat') {
 			if ($room->getType() === Room::ONE_TO_ONE_CALL) {
 				$subject = $l->t('{user} sent you a private message');
+			} else if ($richSubjectUser) {
+				$subject = $l->t('{user} sent a message in conversation {call}');
+			} else if (!$isGuest) {
+				$subject = $l->t('A deleted user sent a message in conversation {call}');
 			} else {
-				if ($richSubjectUser) {
-					$subject = $l->t('{user} sent a message in conversation {call}');
-				} else if (!$isGuest) {
-					$subject = $l->t('A deleted user sent a message in conversation {call}');
-				} else {
-					$subject = $l->t('A guest sent a message in conversation {call}');
-				}
+				$subject = $l->t('A guest sent a message in conversation {call}');
 			}
-		} else if ($room->getType() === Room::ONE_TO_ONE_CALL) {
-			$subject = $l->t('{user} mentioned you in a private conversation');
-		} else {
-			if ($richSubjectUser) {
-				$subject = $l->t('{user} mentioned you in conversation {call}');
+		} else if ($notification->getSubject() === 'reply') {
+			if ($room->getType() === Room::ONE_TO_ONE_CALL) {
+				$subject = $l->t('{user} replied to your private message');
+			} else if ($richSubjectUser) {
+				$subject = $l->t('{user} replied to your message in conversation {call}');
 			} else if (!$isGuest) {
-				$subject = $l->t('A deleted user mentioned you in conversation {call}');
+				$subject = $l->t('A deleted user replied to your message in conversation {call}');
 			} else {
-				$subject = $l->t('A guest mentioned you in conversation {call}');
+				$subject = $l->t('A guest replied to your message in conversation {call}');
 			}
+		} else if ($room->getType() === Room::ONE_TO_ONE_CALL) {
+			$subject = $l->t('{user} mentioned you in a private conversation');
+		} else if ($richSubjectUser) {
+			$subject = $l->t('{user} mentioned you in conversation {call}');
+		} else if (!$isGuest) {
+			$subject = $l->t('A deleted user mentioned you in conversation {call}');
+		} else {
+			$subject = $l->t('A guest mentioned you in conversation {call}');
 		}
 		$notification = $this->addActionButton($notification, $l->t('View chat'), false);
 
diff --git a/tests/integration/features/bootstrap/FeatureContext.php b/tests/integration/features/bootstrap/FeatureContext.php
index 62e17349ad1..ec4a08f9788 100644
--- a/tests/integration/features/bootstrap/FeatureContext.php
+++ b/tests/integration/features/bootstrap/FeatureContext.php
@@ -39,6 +39,8 @@ class FeatureContext implements Context, SnippetAcceptingContext {
 	protected static $tokenToIdentifier;
 	/** @var array[] */
 	protected static $sessionIdToUser;
+	/** @var array[] */
+	protected static $messages;
 
 	/** @var string */
 	protected $currentUser;
@@ -80,6 +82,7 @@ public function setUp() {
 		self::$identifierToToken = [];
 		self::$tokenToIdentifier = [];
 		self::$sessionIdToUser = [];
+		self::$messages = [];
 
 		$this->createdUsers = [];
 		$this->createdGroups = [];
@@ -582,6 +585,37 @@ public function userSendsMessageToRoom($user, $message, $identifier, $statusCode
 		);
 		$this->assertStatusCode($this->response, $statusCode);
 		sleep(1); // make sure Postgres manages the order of the messages
+
+		$response = $this->getDataFromResponse($this->response);
+		if (isset($response['id'])) {
+			self::$messages[$message] = $response['id'];
+		}
+	}
+
+	/**
+	 * @Then /^user "([^"]*)" sends reply "([^"]*)" on message "([^"]*)" to room "([^"]*)" with (\d+)$/
+	 *
+	 * @param string $user
+	 * @param string $reply
+	 * @param string $message
+	 * @param string $identifier
+	 * @param string $statusCode
+	 */
+	public function userSendsReplyToRoom($user, $reply, $message, $identifier, $statusCode) {
+		$replyTo = self::$messages[$message];
+
+		$this->setCurrentUser($user);
+		$this->sendRequest(
+			'POST', '/apps/spreed/api/v1/chat/' . self::$identifierToToken[$identifier],
+			new TableNode([['message', $reply], ['replyTo', $replyTo]])
+		);
+		$this->assertStatusCode($this->response, $statusCode);
+		sleep(1); // make sure Postgres manages the order of the messages
+
+		$response = $this->getDataFromResponse($this->response);
+		if (isset($response['id'])) {
+			self::$messages[$reply] = $response['id'];
+		}
 	}
 
 	/**
@@ -605,23 +639,40 @@ public function userSeesTheFollowingMessagesInRoom($user, $identifier, $statusCo
 			}
 		}, $actual);
 
+		foreach ($messages as $message) {
+			// Include the received messages in the list of messages used for
+			// replies; this is needed to get special messages not explicitly
+			// sent like those for shared files.
+			self::$messages[$message['message']] = $message['id'];
+		}
+
 		if ($formData === null) {
 			PHPUnit_Framework_Assert::assertEmpty($messages);
 			return;
 		}
+		$includeParents = in_array('parentMessage', $formData->getRow(0), true);
 
 		PHPUnit_Framework_Assert::assertCount(count($formData->getHash()), $messages, 'Message count does not match');
-		PHPUnit_Framework_Assert::assertEquals($formData->getHash(), array_map(function($message) {
-			return [
+		for ($i = 0; $i < count($formData->getHash()); $i++) {
+			if ($formData->getHash()[$i]['messageParameters'] === '"IGNORE"') {
+				$messages[$i]['messageParameters'] = 'IGNORE';
+			}
+		}
+		PHPUnit_Framework_Assert::assertEquals($formData->getHash(), array_map(function($message) use($includeParents) {
+			$data = [
 				'room' => self::$tokenToIdentifier[$message['token']],
-				'actorType' => (string) $message['actorType'],
-				'actorId' => ($message['actorType'] === 'guests')? self::$sessionIdToUser[$message['actorId']]: (string) $message['actorId'],
-				'actorDisplayName' => (string) $message['actorDisplayName'],
+				'actorType' => $message['actorType'],
+				'actorId' => ($message['actorType'] === 'guests')? self::$sessionIdToUser[$message['actorId']]: $message['actorId'],
+				'actorDisplayName' => $message['actorDisplayName'],
 				// TODO test timestamp; it may require using Runkit, php-timecop
 				// or something like that.
-				'message' => (string) $message['message'],
+				'message' => $message['message'],
 				'messageParameters' => json_encode($message['messageParameters']),
 			];
+			if ($includeParents) {
+				$data['parentMessage'] = $message['parent']['message'] ?? '';
+			}
+			return $data;
 		}, $messages));
 	}
 
@@ -642,6 +693,12 @@ public function userSeesTheFollowingSystemMessagesInRoom($user, $identifier, $st
 			return $message['systemMessage'] !== '';
 		});
 
+		foreach ($messages as $systemMessage) {
+			// Include the received system messages in the list of messages used
+			// for replies.
+			self::$messages[$systemMessage['systemMessage']] = $systemMessage['id'];
+		}
+
 		if ($formData === null) {
 			PHPUnit_Framework_Assert::assertEmpty($messages);
 			return;
diff --git a/tests/integration/features/chat/reply.feature b/tests/integration/features/chat/reply.feature
new file mode 100644
index 00000000000..4a8c9a56ec1
--- /dev/null
+++ b/tests/integration/features/chat/reply.feature
@@ -0,0 +1,215 @@
+Feature: chat/reply
+  Background:
+    Given user "participant1" exists
+    Given user "participant2" exists
+    Given user "participant3" exists
+    And group "attendees1" exists
+    And user "participant2" is member of group "attendees1"
+
+  Scenario: user can reply to own message
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    When user "participant1" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+
+  Scenario: user can reply to other's messages
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    When user "participant2" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+
+  Scenario: several users can reply to the same message several times
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    When user "participant1" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-2" on message "Message 1" to room "group room" with 201
+    And user "participant1" sends reply "Message 1-3" on message "Message 1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-4" on message "Message 1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-4 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1-3 | []                | Message 1     |
+      | group room | users     | participant2 | participant2-displayname | Message 1-2 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-4 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1-3 | []                | Message 1     |
+      | group room | users     | participant2 | participant2-displayname | Message 1-2 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1 | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1   | []                |               |
+
+
+
+  Scenario: user can reply to shared file messages
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" shares "welcome.txt" with room "group room"
+    # The messages need to be got so the file message is added to the list of
+    # known messages to reply to.
+    # The file message parameters are not relevant for this test and are quite
+    # large, so they are simply ignored.
+    And user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | {file}  | "IGNORE"          |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | {file}  | "IGNORE"          |               |
+    When user "participant1" sends reply "Message X-1" on message "{file}" to room "group room" with 201
+    And user "participant2" sends reply "Message X-2" on message "{file}" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message X-2 | []                | {file}        |
+      | group room | users     | participant1 | participant1-displayname | Message X-1 | []                | {file}        |
+      | group room | users     | participant1 | participant1-displayname | {file}      | "IGNORE"          |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message     | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message X-2 | []                | {file}        |
+      | group room | users     | participant1 | participant1-displayname | Message X-1 | []                | {file}        |
+      | group room | users     | participant1 | participant1-displayname | {file}      | "IGNORE"          |               |
+
+  Scenario: user can not reply to commands
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "/help" to room "group room" with 201
+    # In the tests the reference for the message to reply to is got from the
+    # messages originally sent, not from how they are returned by the server.
+    When user "participant1" sends reply "Message X-1" on message "/help" to room "group room" with 400
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId | actorDisplayName | message                                    | messageParameters | parentMessage |
+      | group room | bots      | talk    | talk-bot         | There are currently no commands available. | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+
+  Scenario: user can not reply to system messages
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    # The system messages need to be got so they are added to the list of known
+    # messages to reply to.
+    And user "participant1" sees the following system messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | systemMessage        |
+      | group room | users     | participant1 | participant1-displayname | user_added           |
+      | group room | users     | participant1 | participant1-displayname | conversation_created |
+    When user "participant1" sends reply "Message X-1" on message "conversation_created" to room "group room" with 400
+    Then user "participant1" sees the following messages in room "group room" with 200
+    And user "participant2" sees the following messages in room "group room" with 200
+
+
+
+  Scenario: user can reply to own replies
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    And user "participant1" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    When user "participant1" sends reply "Message 1-1-1" on message "Message 1-1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message       | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1   | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1     | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message       | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1   | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1     | []                |               |
+
+  Scenario: user can reply to other's replies
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    When user "participant1" sends reply "Message 1-1-1" on message "Message 1-1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-1-1-1" on message "Message 1-1-1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message         | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-1-1 | []                | Message 1-1-1 |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1   | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1     | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1       | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message         | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-1-1 | []                | Message 1-1-1 |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1   | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1     | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1       | []                |               |
+
+  Scenario: several users can reply to the same reply several times
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-1" on message "Message 1" to room "group room" with 201
+    When user "participant1" sends reply "Message 1-1-1" on message "Message 1-1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-1-2" on message "Message 1-1" to room "group room" with 201
+    And user "participant1" sends reply "Message 1-1-3" on message "Message 1-1" to room "group room" with 201
+    And user "participant2" sends reply "Message 1-1-4" on message "Message 1-1" to room "group room" with 201
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message       | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-4 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-3 | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-2 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1 | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1   | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1     | []                |               |
+    And user "participant2" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message       | messageParameters | parentMessage |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-4 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-3 | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1-2 | []                | Message 1-1   |
+      | group room | users     | participant1 | participant1-displayname | Message 1-1-1 | []                | Message 1-1   |
+      | group room | users     | participant2 | participant2-displayname | Message 1-1   | []                | Message 1     |
+      | group room | users     | participant1 | participant1-displayname | Message 1     | []                |               |
+
+
+
+  Scenario: user can not reply when not in the room
+    Given user "participant1" creates room "group room"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room" with 201
+    When user "participant3" sends reply "Message 1-1" on message "Message 1" to room "group room" with 404
+    Then user "participant1" sees the following messages in room "group room" with 200
+      | room       | actorType | actorId      | actorDisplayName         | message   | messageParameters | parentMessage |
+      | group room | users     | participant1 | participant1-displayname | Message 1 | []                |               |
+    And user "participant3" sees the following messages in room "group room" with 404
+
+
+
+  Scenario: user can not reply to a message from another room
+    Given user "participant1" creates room "group room1"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" creates room "group room2"
+      | roomType | 2 |
+      | invite   | attendees1 |
+    And user "participant1" sends message "Message 1" to room "group room1" with 201
+    When user "participant1" sends reply "Message 1-1" on message "Message 1" to room "group room2" with 400
+    Then user "participant1" sees the following messages in room "group room1" with 200
+      | room        | actorType | actorId      | actorDisplayName         | message   | messageParameters |
+      | group room1 | users     | participant1 | participant1-displayname | Message 1 | []                |
+    And user "participant1" sees the following messages in room "group room2" with 200
diff --git a/tests/php/Chat/ChatManagerTest.php b/tests/php/Chat/ChatManagerTest.php
index ab8774fe836..8398b7596ee 100644
--- a/tests/php/Chat/ChatManagerTest.php
+++ b/tests/php/Chat/ChatManagerTest.php
@@ -118,7 +118,54 @@ public function testSendMessage() {
 
 		$participant = $this->createMock(Participant::class);
 
-		$this->chatManager->sendMessage($chat, $participant, 'users', 'testUser', 'testMessage', $creationDateTime);
+		$this->chatManager->sendMessage($chat, $participant, 'users', 'testUser', 'testMessage', $creationDateTime, null);
+	}
+
+	public function testReplyToMessage() {
+		$replyTo = $this->createMock(IComment::class);
+		$comment = $this->createMock(IComment::class);
+
+		$this->commentsManager->expects($this->once())
+			->method('create')
+			->with('users', 'testUser', 'chat', 1234)
+			->willReturn($comment);
+
+		$comment->expects($this->once())
+			->method('setMessage')
+			->with('testMessage');
+
+		$creationDateTime = new \DateTime();
+		$comment->expects($this->once())
+			->method('setCreationDateTime')
+			->with($creationDateTime);
+
+		$comment->expects($this->once())
+			->method('setVerb')
+			->with('comment');
+
+		$this->commentsManager->expects($this->once())
+			->method('save')
+			->with($comment);
+
+		$chat = $this->createMock(Room::class);
+		$chat->expects($this->any())
+			->method('getId')
+			->willReturn(1234);
+
+		$this->notifier->expects($this->once())
+			->method('notifyMentionedUsers')
+			->with($chat, $comment);
+
+		$replyTo->expects($this->once())
+			->method('getId')
+			->willReturn('12345');
+
+		$comment->expects($this->once())
+			->method('setParentId')
+			->with('12345');
+
+		$participant = $this->createMock(Participant::class);
+		$this->chatManager->sendMessage($chat, $participant, 'users', 'testUser', 'testMessage', $creationDateTime, $replyTo);
 	}
 
 	public function testGetHistory() {
diff --git a/tests/php/Chat/NotifierTest.php b/tests/php/Chat/NotifierTest.php
index 3c4941d56fb..0037a76ccf7 100644
--- a/tests/php/Chat/NotifierTest.php
+++ b/tests/php/Chat/NotifierTest.php
@@ -174,7 +174,35 @@ public function testNotifyMentionedUsers() {
 			->method('notify')
 			->with($notification);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
+	}
+
+	public function testNotNotifyMentionedUserIfReplyToAuthor() {
+		$comment = $this->newComment(108, 'users', 'testUser', new \DateTime('@' . 1000000016), 'Mention @anotherUser');
+
+		$room = $this->createMock(Room::class);
+		$room->expects($this->any())
+			->method('getToken')
+			->willReturn('Token123');
+
+		$notification = $this->newNotification($room, $comment);
+
+		$this->notificationManager->expects($this->once())
+			->method('createNotification')
+			->willReturn($notification);
+
+		$notification->expects($this->never())
+			->method('setUser');
+
+		$notification->expects($this->once())
+			->method('setMessage')
+			->with('comment')
+			->willReturnSelf();
+
+		$this->notificationManager->expects($this->never())
+			->method('notify');
+
+		$this->notifier->notifyMentionedUsers($room, $comment, ['anotherUser']);
 	}
 
 	public function testNotifyMentionedUsersByGuest() {
@@ -217,7 +245,7 @@ public function testNotifyMentionedUsersByGuest() {
 			->method('notify')
 			->with($notification);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersWithLongMessageStartMention() {
@@ -261,7 +289,7 @@ public function testNotifyMentionedUsersWithLongMessageStartMention() {
 			->method('notify')
 			->with($notification);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersWithLongMessageMiddleMention() {
@@ -305,7 +333,7 @@ public function testNotifyMentionedUsersWithLongMessageMiddleMention() {
 			->method('notify')
 			->with($notification);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersWithLongMessageEndMention() {
@@ -349,7 +377,7 @@ public function testNotifyMentionedUsersWithLongMessageEndMention() {
 			->method('notify')
 			->with($notification);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersToSelf() {
@@ -369,7 +397,7 @@ public function testNotifyMentionedUsersToSelf() {
 		$this->notificationManager->expects($this->never())
 			->method('notify');
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersToUnknownUser() {
@@ -390,7 +418,7 @@ public function testNotifyMentionedUsersToUnknownUser() {
 		$this->notificationManager->expects($this->never())
 			->method('notify');
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersToUserNotInvitedToChat() {
@@ -421,7 +449,7 @@ public function testNotifyMentionedUsersToUserNotInvitedToChat() {
 		$this->notificationManager->expects($this->never())
 			->method('notify');
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersNoMentions() {
@@ -438,7 +466,7 @@ public function testNotifyMentionedUsersNoMentions() {
 		$this->notificationManager->expects($this->never())
 			->method('notify');
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testNotifyMentionedUsersSeveralMentions() {
@@ -487,7 +515,7 @@ public function testNotifyMentionedUsersSeveralMentions() {
 				[ $notification ]
 			);
 
-		$this->notifier->notifyMentionedUsers($room, $comment);
+		$this->notifier->notifyMentionedUsers($room, $comment, []);
 	}
 
 	public function testRemovePendingNotificationsForRoom() {
diff --git a/tests/php/Chat/Parser/SystemMessageTest.php b/tests/php/Chat/Parser/SystemMessageTest.php
index 57234c74a39..32ecfcc9f58 100644
--- a/tests/php/Chat/Parser/SystemMessageTest.php
+++ b/tests/php/Chat/Parser/SystemMessageTest.php
@@ -368,17 +368,13 @@ public function testParseMessage(string $message, array $parameters, $recipientI
 				->method('getFileFromShare');
 		}
 
-		$comment->expects($this->once())
-			->method('setMessage')
-			->with($message);
-
 		/** @var Room|MockObject $room */
 		$room = $this->createMock(Room::class);
 		$chatMessage = new Message($room, $participant, $comment, $this->l);
 		$chatMessage->setMessage(json_encode([
 			'message' => $message,
 			'parameters' => $parameters,
-		]), []);
+		]), [], $message);
 
 		$parser->parseMessage($chatMessage);
 
diff --git a/tests/php/Controller/ChatControllerTest.php b/tests/php/Controller/ChatControllerTest.php
index 6e9b82b1ffd..6364617c40c 100644
--- a/tests/php/Controller/ChatControllerTest.php
+++ b/tests/php/Controller/ChatControllerTest.php
@@ -136,6 +136,7 @@ private function newComment($id, $actorType, $actorId, $creationDateTime, $messa
 		$comment->method('getActorId')->willReturn($actorId);
 		$comment->method('getCreationDateTime')->willReturn($creationDateTime);
 		$comment->method('getMessage')->willReturn($message);
+		$comment->method('getParentId')->willReturn('0');
 
 		return $comment;
 	}
@@ -179,12 +180,18 @@ public function testSendMessageByUser() {
 		$chatMessage->expects($this->once())
 			->method('getMessageParameters')
 			->willReturn(['arg' => 'uments']);
-		$chatMessage->expects($this->once())
+		$chatMessage->expects($this->exactly(2))
 			->method('getMessageType')
 			->willReturn('comment');
 		$chatMessage->expects($this->once())
 			->method('getVisibility')
 			->willReturn(true);
+		$chatMessage->expects($this->exactly(2))
+			->method('getComment')
+			->willReturn($comment);
+		$chatMessage->expects($this->once())
+			->method('getRoom')
+			->willReturn($this->room);
 
 		$this->messageParser->expects($this->once())
 			->method('createMessage')
@@ -208,11 +215,214 @@ public function testSendMessageByUser() {
 			'message' => 'parsedMessage',
 			'messageParameters' => ['arg' => 'uments'],
 			'systemMessage' => '',
+			'messageType' => 'comment',
+		], Http::STATUS_CREATED);
+
+		$this->assertEquals($expected, $response);
+	}
+
+	public function testSendReplyByUser() {
+		$participant = $this->createMock(Participant::class);
+		$this->room->expects($this->exactly(2))
+			->method('getToken')
+			->willReturn('testToken');
+
+		$date = new \DateTime();
+		$this->timeFactory->expects($this->once())
+			->method('getDateTime')
+			->willReturn($date);
+
+		/** @var IComment|MockObject $comment */
+		$parent = $this->newComment(23, 'user', $this->userId . '2', $date, 'testMessage original');
+
+		/** @var IComment|MockObject $comment */
+		$comment = $this->newComment(42, 'user', $this->userId, $date, 'testMessage');
+		$this->chatManager->expects($this->once())
+			->method('sendMessage')
+			->with($this->room,
+				$participant,
+				'users',
+				$this->userId,
+				'testMessage',
+				$this->newMessageDateTimeConstraint,
+				$parent
+			)
+			->willReturn($comment);
+		$this->chatManager->expects($this->once())
+			->method('getParentComment')
+			->with($this->room, 23)
+			->willReturn($parent);
+
+		$parentMessage = $this->createMock(Message::class);
+		$parentMessage->expects($this->once())
+			->method('getActorType')
+			->willReturn('user');
+		$parentMessage->expects($this->once())
+			->method('getActorId')
+			->willReturn($this->userId . '2');
+		$parentMessage->expects($this->once())
+			->method('getActorDisplayName')
+			->willReturn('displayName2');
+		$parentMessage->expects($this->once())
+			->method('getMessage')
+			->willReturn('parsedMessage2');
+		$parentMessage->expects($this->once())
+			->method('getMessageParameters')
+			->willReturn(['arg' => 'uments2']);
+		$parentMessage->expects($this->exactly(4))
+			->method('getMessageType')
+			->willReturn('comment');
+		$parentMessage->expects($this->exactly(2))
+			->method('getComment')
+			->willReturn($parent);
+		$parentMessage->expects($this->once())
+			->method('getRoom')
+			->willReturn($this->room);
+
+		$chatMessage = $this->createMock(Message::class);
+		$chatMessage->expects($this->once())
+			->method('getActorType')
+			->willReturn('user');
+		$chatMessage->expects($this->once())
+			->method('getActorId')
+			->willReturn($this->userId);
+		$chatMessage->expects($this->once())
+			->method('getActorDisplayName')
+			->willReturn('displayName');
+		$chatMessage->expects($this->once())
+			->method('getMessage')
+			->willReturn('parsedMessage');
+		$chatMessage->expects($this->once())
+			->method('getMessageParameters')
+			->willReturn(['arg' => 'uments']);
+		$chatMessage->expects($this->exactly(2))
+			->method('getMessageType')
+			->willReturn('comment');
+		$chatMessage->expects($this->once())
+			->method('getVisibility')
+			->willReturn(true);
+		$chatMessage->expects($this->exactly(2))
+			->method('getComment')
+			->willReturn($comment);
+		$chatMessage->expects($this->once())
+			->method('getRoom')
+			->willReturn($this->room);
+
+		$this->messageParser->expects($this->exactly(2))
+			->method('createMessage')
+			->withConsecutive(
+				[$this->room, $participant, $parent, $this->l],
+				[$this->room, $participant, $comment, $this->l]
+			)
+			->willReturnOnConsecutiveCalls($parentMessage, $chatMessage);
+
+		$this->messageParser->expects($this->exactly(2))
+			->method('parseMessage')
+			->withConsecutive([$parentMessage], [$chatMessage]);
+
+		$this->controller->setRoom($this->room);
+		$this->controller->setParticipant($participant);
+		$response = $this->controller->sendMessage('testMessage', '', 23);
+		$expected = new DataResponse([
+			'id' => 42,
+			'token' => 'testToken',
+			'actorType' => 'user',
+			'actorId' => $this->userId,
+			'actorDisplayName' => 'displayName',
+			'timestamp' => $date->getTimestamp(),
+			'message' => 'parsedMessage',
+			'messageParameters' => ['arg' => 'uments'],
+			'systemMessage' => '',
+			'messageType' => 'comment',
+			'parent' => [
+				'id' => 23,
+				'token' => 'testToken',
+				'actorType' => 'user',
+				'actorId' => $this->userId . '2',
+				'actorDisplayName' => 'displayName2',
+				'timestamp' => $date->getTimestamp(),
+				'message' => 'parsedMessage2',
+				'messageParameters' => ['arg' => 'uments2'],
+				'systemMessage' => '',
+				'messageType' => 'comment',
+			]
 		], Http::STATUS_CREATED);
 
 		$this->assertEquals($expected, $response);
 	}
 
+	public function testSendReplyByUserToCommand() {
+		$participant = $this->createMock(Participant::class);
+
+		$date = new \DateTime();
+		/** @var IComment|MockObject $comment */
+		$parent = $this->newComment(23, 'user', $this->userId . '2', $date, 'testMessage original');
+
+		$this->chatManager->expects($this->never())
+			->method('sendMessage');
+		$this->chatManager->expects($this->once())
+			->method('getParentComment')
+			->with($this->room, 23)
+			->willReturn($parent);
+
+		$parentMessage = $this->createMock(Message::class);
+		$parentMessage->expects($this->exactly(2))
+			->method('getMessageType')
+			->willReturn('command');
+
+		$this->messageParser->expects($this->once())
+			->method('createMessage')
+			->with($this->room, $participant, $parent, $this->l)
+			->willReturn($parentMessage);
+
+		$this->messageParser->expects($this->once())
+			->method('parseMessage')
+			->with($parentMessage);
+
+		$this->controller->setRoom($this->room);
+		$this->controller->setParticipant($participant);
+		$response = $this->controller->sendMessage('testMessage', '', 23);
+		$expected = new DataResponse([], Http::STATUS_BAD_REQUEST);
+
+		$this->assertEquals($expected, $response);
+	}
+
+	public function testSendReplyByUserToSystemMessage() {
+		$participant = $this->createMock(Participant::class);
+
+		$date = new \DateTime();
+		/** @var IComment|MockObject $comment */
+		$parent = $this->newComment(23, 'user', $this->userId . '2', $date, 'testMessage original');
+
+		$this->chatManager->expects($this->never())
+			->method('sendMessage');
+		$this->chatManager->expects($this->once())
+			->method('getParentComment')
+			->with($this->room, 23)
+			->willReturn($parent);
+
+		$parentMessage = $this->createMock(Message::class);
+		$parentMessage->expects($this->once())
+			->method('getMessageType')
+			->willReturn('system');
+
+		$this->messageParser->expects($this->once())
+			->method('createMessage')
+			->with($this->room, $participant, $parent, $this->l)
+			->willReturn($parentMessage);
+
+		$this->messageParser->expects($this->once())
+			->method('parseMessage')
+			->with($parentMessage);
+
+		$this->controller->setRoom($this->room);
+		$this->controller->setParticipant($participant);
+		$response = $this->controller->sendMessage('testMessage', '', 23);
+		$expected = new DataResponse([], Http::STATUS_BAD_REQUEST);
+
+		$this->assertEquals($expected, $response);
+	}
+
 	public function testSendMessageByUserNotJoinedButInRoom() {
 		$participant = $this->createMock(Participant::class);
 		$this->room->expects($this->once())
@@ -252,12 +462,18 @@ public function testSendMessageByUserNotJoinedButInRoom() {
 		$chatMessage->expects($this->once())
 			->method('getMessageParameters')
 			->willReturn(['arg' => 'uments2']);
-		$chatMessage->expects($this->once())
+		$chatMessage->expects($this->exactly(2))
 			->method('getMessageType')
 			->willReturn('comment');
 		$chatMessage->expects($this->once())
 			->method('getVisibility')
 			->willReturn(true);
+		$chatMessage->expects($this->exactly(2))
+			->method('getComment')
+			->willReturn($comment);
+		$chatMessage->expects($this->once())
+			->method('getRoom')
+			->willReturn($this->room);
 
 		$this->messageParser->expects($this->once())
 			->method('createMessage')
@@ -281,6 +497,7 @@ public function testSendMessageByUserNotJoinedButInRoom() {
 			'message' => 'parsedMessage2',
 			'messageParameters' => ['arg' => 'uments2'],
 			'systemMessage' => '',
+			'messageType' => 'comment',
 		], Http::STATUS_CREATED);
 
 		$this->assertEquals($expected, $response);
@@ -333,12 +550,18 @@ public function testSendMessageByGuest() {
 		$chatMessage->expects($this->once())
 			->method('getMessageParameters')
 			->willReturn(['arg' => 'uments3']);
-		$chatMessage->expects($this->once())
+		$chatMessage->expects($this->exactly(2))
 			->method('getMessageType')
 			->willReturn('comment');
 		$chatMessage->expects($this->once())
 			->method('getVisibility')
 			->willReturn(true);
+		$chatMessage->expects($this->exactly(2))
+			->method('getComment')
+			->willReturn($comment);
+		$chatMessage->expects($this->once())
+			->method('getRoom')
+			->willReturn($this->room);
 
 		$this->messageParser->expects($this->once())
 			->method('createMessage')
@@ -362,6 +585,7 @@ public function testSendMessageByGuest() {
 			'message' => 'parsedMessage3',
 			'messageParameters' => ['arg' => 'uments3'],
 			'systemMessage' => '',
+			'messageType' => 'comment',
 		], Http::STATUS_CREATED);
 
 		$this->assertEquals($expected, $response);
@@ -411,12 +635,18 @@ public function testReceiveHistoryByUser() {
 				$chatMessage->expects($this->once())
 					->method('getMessageParameters')
 					->willReturn(['testMessageParameters' . $i]);
-				$chatMessage->expects($this->once())
+				$chatMessage->expects($this->exactly(2))
 					->method('getMessageType')
 					->willReturn('comment');
 				$chatMessage->expects($this->once())
 					->method('getVisibility')
 					->willReturn(true);
+				$chatMessage->expects($this->atLeastOnce())
+					->method('getComment')
+					->willReturn($comment);
+				$chatMessage->expects($this->once())
+					->method('getRoom')
+					->willReturn($room);
 
 				$i--;
 				return $chatMessage;
@@ -429,10 +659,10 @@ public function testReceiveHistoryByUser() {
 		$this->controller->setParticipant($participant);
 		$response = $this->controller->receiveMessages(0, $limit, $offset);
 		$expected = new DataResponse([
-			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => ''],
-			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => ''],
-			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => ''],
-			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '']
+			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '', 'messageType' => 'comment']
 		], Http::STATUS_OK);
 		$expected->addHeader('X-Chat-Last-Given', 108);
 
@@ -483,12 +713,18 @@ public function testReceiveMessagesByUserNotJoinedButInRoom() {
 				$chatMessage->expects($this->once())
 					->method('getMessageParameters')
 					->willReturn(['testMessageParameters' . $i]);
-				$chatMessage->expects($this->once())
+				$chatMessage->expects($this->exactly(2))
 					->method('getMessageType')
 					->willReturn('comment');
 				$chatMessage->expects($this->once())
 					->method('getVisibility')
 					->willReturn(true);
+				$chatMessage->expects($this->atLeastOnce())
+					->method('getComment')
+					->willReturn($comment);
+				$chatMessage->expects($this->once())
+					->method('getRoom')
+					->willReturn($room);
 
 				$i--;
 				return $chatMessage;
@@ -501,10 +737,10 @@ public function testReceiveMessagesByUserNotJoinedButInRoom() {
 		$this->controller->setParticipant($participant);
 		$response = $this->controller->receiveMessages(0, $limit, $offset);
 		$expected = new DataResponse([
-			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => ''],
-			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => ''],
-			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => ''],
-			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '']
+			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '', 'messageType' => 'comment']
 		], Http::STATUS_OK);
 		$expected->addHeader('X-Chat-Last-Given', 108);
 
@@ -558,12 +794,18 @@ public function testReceiveMessagesByGuest() {
 				$chatMessage->expects($this->once())
 					->method('getMessageParameters')
 					->willReturn(['testMessageParameters' . $i]);
-				$chatMessage->expects($this->once())
+				$chatMessage->expects($this->exactly(2))
 					->method('getMessageType')
 					->willReturn('comment');
 				$chatMessage->expects($this->once())
 					->method('getVisibility')
 					->willReturn(true);
+				$chatMessage->expects($this->atLeastOnce())
+					->method('getComment')
+					->willReturn($comment);
+				$chatMessage->expects($this->once())
+					->method('getRoom')
+					->willReturn($room);
 
 				$i--;
 				return $chatMessage;
@@ -576,10 +818,10 @@ public function testReceiveMessagesByGuest() {
 		$this->controller->setParticipant($participant);
 		$response = $this->controller->receiveMessages(0, $limit, $offset);
 		$expected = new DataResponse([
-			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => ''],
-			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => ''],
-			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => ''],
-			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '']
+			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '', 'messageType' => 'comment']
 		], Http::STATUS_OK);
 		$expected->addHeader('X-Chat-Last-Given', 108);
 
@@ -641,12 +883,18 @@ public function testWaitForNewMessagesByUser() {
 				$chatMessage->expects($this->once())
 					->method('getMessageParameters')
 					->willReturn(['testMessageParameters' . $i]);
-				$chatMessage->expects($this->once())
+				$chatMessage->expects($this->exactly(2))
 					->method('getMessageType')
 					->willReturn('comment');
 				$chatMessage->expects($this->once())
 					->method('getVisibility')
 					->willReturn(true);
+				$chatMessage->expects($this->atLeastOnce())
+					->method('getComment')
+					->willReturn($comment);
+				$chatMessage->expects($this->once())
+					->method('getRoom')
+					->willReturn($room);
 
 				$i++;
 				return $chatMessage;
@@ -659,10 +907,10 @@ public function testWaitForNewMessagesByUser() {
 		$this->controller->setParticipant($participant);
 		$response = $this->controller->receiveMessages(1, $limit, $offset, $timeout);
 		$expected = new DataResponse([
-			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => ''],
-			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => ''],
-			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => ''],
-			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => ''],
+			['id'=>108, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User1', 'timestamp'=>1000000004, 'message'=>'testMessage1', 'messageParameters'=>['testMessageParameters1'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>109, 'token'=>'testToken', 'actorType'=>'guests', 'actorId'=>'testSpreedSession', 'actorDisplayName'=>'User2', 'timestamp'=>1000000008, 'message'=>'testMessage2', 'messageParameters'=>['testMessageParameters2'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>110, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUnknownUser', 'actorDisplayName'=>'User3', 'timestamp'=>1000000015, 'message'=>'testMessage3', 'messageParameters'=>['testMessageParameters3'], 'systemMessage' => '', 'messageType' => 'comment'],
+			['id'=>111, 'token'=>'testToken', 'actorType'=>'users', 'actorId'=>'testUser', 'actorDisplayName'=>'User4', 'timestamp'=>1000000016, 'message'=>'testMessage4', 'messageParameters'=>['testMessageParameters4'], 'systemMessage' => '', 'messageType' => 'comment'],
 		], Http::STATUS_OK);
 		$expected->addHeader('X-Chat-Last-Given', 111);
 
diff --git a/tests/php/Notification/NotifierTest.php b/tests/php/Notification/NotifierTest.php
index 5247bea0361..64820dc051a 100644
--- a/tests/php/Notification/NotifierTest.php
+++ b/tests/php/Notification/NotifierTest.php
@@ -686,7 +686,7 @@ public function testPrepareChatMessage(bool $isMention, int $roomType, array $su
 		$notification->expects($this->once())
 			->method('getApp')
 			->willReturn('spreed');
-		$notification->expects($this->exactly(2))
+		$notification->expects($this->atLeast(2))
 			->method('getSubject')
 			->willReturn($isMention ? 'mention'  : 'chat');
 		$notification->expects($this->once())