diff --git a/src/Entities/TokenInterface.php b/src/Entities/TokenInterface.php
index e4da51afe..b51fce9d4 100644
--- a/src/Entities/TokenInterface.php
+++ b/src/Entities/TokenInterface.php
@@ -43,9 +43,9 @@ public function setExpiryDateTime(DateTimeImmutable $dateTime): void;
     /**
      * Set the identifier of the user associated with the token.
      *
-     * @param int|non-empty-string $identifier
+     * @param non-empty-string|int $identifier
      */
-    public function setUserIdentifier(int|string $identifier): void;
+    public function setUserIdentifier(string|int $identifier): void;
 
     /**
      * Get the token user's identifier.
diff --git a/src/Grant/AbstractGrant.php b/src/Grant/AbstractGrant.php
index 057d86593..3e71800b4 100644
--- a/src/Grant/AbstractGrant.php
+++ b/src/Grant/AbstractGrant.php
@@ -184,7 +184,7 @@ protected function validateClient(ServerRequestInterface $request): ClientEntity
      * getClientEntity might return null. By contrast, this method will
      * always either return a ClientEntityInterface or throw.
      */
-    protected function getClientEntityOrFail(string $clientId, ServerRequestInterface $request): ClientEntityInterface
+    protected function getClientEntityOrFail(string|int $clientId, ServerRequestInterface $request): ClientEntityInterface
     {
         $client = $this->clientRepository->getClientEntity($clientId);
 
diff --git a/src/Repositories/AccessTokenRepositoryInterface.php b/src/Repositories/AccessTokenRepositoryInterface.php
index d392716ed..254456e86 100644
--- a/src/Repositories/AccessTokenRepositoryInterface.php
+++ b/src/Repositories/AccessTokenRepositoryInterface.php
@@ -30,7 +30,7 @@ interface AccessTokenRepositoryInterface extends RepositoryInterface
     public function getNewToken(
         ClientEntityInterface $clientEntity,
         array $scopes,
-        mixed $userIdentifier = null
+        string|int|null $userIdentifier = null
     ): AccessTokenEntityInterface;
 
     /**
diff --git a/src/Repositories/ClientRepositoryInterface.php b/src/Repositories/ClientRepositoryInterface.php
index 63134ca9d..79420166f 100644
--- a/src/Repositories/ClientRepositoryInterface.php
+++ b/src/Repositories/ClientRepositoryInterface.php
@@ -22,10 +22,10 @@ interface ClientRepositoryInterface extends RepositoryInterface
     /**
      * Get a client.
      */
-    public function getClientEntity(string $clientIdentifier): ?ClientEntityInterface;
+    public function getClientEntity(string|int $clientIdentifier): ?ClientEntityInterface;
 
     /**
      * Validate a client's secret.
      */
-    public function validateClient(string $clientIdentifier, ?string $clientSecret, ?string $grantType): bool;
+    public function validateClient(string|int $clientIdentifier, ?string $clientSecret, ?string $grantType): bool;
 }