diff --git a/system/HTTP/Message.php b/system/HTTP/Message.php
index 68fc59a8a4b3..793ed5642c17 100644
--- a/system/HTTP/Message.php
+++ b/system/HTTP/Message.php
@@ -142,7 +142,14 @@ public function getProtocolVersion(): string
 	 */
 	public function isJSON()
 	{
-		return $this->hasHeader('Content-Type')
-			&& $this->header('Content-Type')->getValue() === 'application/json';
+		if (! $this->hasHeader('Content-Type'))
+		{
+			return false;
+		}
+
+		$header = $this->header('Content-Type')->getValue();
+		$parts  = explode(';', $header);
+
+		return in_array('application/json', $parts, true);
 	}
 }
diff --git a/tests/system/HTTP/MessageTest.php b/tests/system/HTTP/MessageTest.php
index d2bc8aa7f89a..3972a63fdd33 100644
--- a/tests/system/HTTP/MessageTest.php
+++ b/tests/system/HTTP/MessageTest.php
@@ -349,4 +349,10 @@ public function testIsJsonReturnsTrue()
 		$this->assertTrue($this->message->isJSON());
 	}
 
+	public function testIsJsonWorksWithExtendedContentType()
+	{
+		$this->message->setHeader('Content-Type', 'application/json;charset=UTF-8');
+		$this->assertTrue($this->message->isJSON());
+	}
+
 }