diff --git a/lib/Chat/ChatManager.php b/lib/Chat/ChatManager.php
index 33eb200f177..0869bdac642 100644
--- a/lib/Chat/ChatManager.php
+++ b/lib/Chat/ChatManager.php
@@ -483,10 +483,25 @@ public function deleteMessage(Room $chat, IComment $comment, Participant $partic
 	 * @param \DateTime $editTime
 	 * @param string $message
 	 * @return IComment
+	 * @throws \InvalidArgumentException When the message is empty or the shared object is not a file share with caption
 	 */
 	public function editMessage(Room $chat, IComment $comment, Participant $participant, \DateTime $editTime, string $message): IComment {
-		// FIXME "Caption" handling via $comment->getVerb() === self::VERB_OBJECT_SHARED
-		// TODO prevent editing other shares like polls, contacts, etc.
+		if (trim($message) === '') {
+			throw new \InvalidArgumentException('message');
+		}
+
+		if ($comment->getVerb() === ChatManager::VERB_OBJECT_SHARED) {
+			$messageData = json_decode($comment->getMessage(), true);
+			if (!isset($messageData['message']) || $messageData['message'] !== 'file_shared') {
+				// Not a file share
+				throw new \InvalidArgumentException('object_share');
+			}
+
+			$messageData['parameters'] ??= [];
+			$messageData['parameters']['metaData'] ??= [];
+			$messageData['parameters']['metaData']['caption'] = $message;
+			$message = json_encode($messageData);
+		}
 
 		$metaData = $comment->getMetaData() ?? [];
 		$metaData['last_edited_by_type'] = $participant->getAttendee()->getActorType();
diff --git a/lib/Controller/ChatController.php b/lib/Controller/ChatController.php
index 914535ce9c0..0381e042cb0 100644
--- a/lib/Controller/ChatController.php
+++ b/lib/Controller/ChatController.php
@@ -753,11 +753,11 @@ public function deleteMessage(int $messageId): DataResponse {
 	 * @param int $messageId ID of the message
 	 * @param string $message the message to send
 	 * @psalm-param non-negative-int $messageId
-	 * @return DataResponse<Http::STATUS_OK|Http::STATUS_ACCEPTED, TalkChatMessageWithParent, array{X-Chat-Last-Common-Read?: numeric-string}>|DataResponse<Http::STATUS_BAD_REQUEST|Http::STATUS_FORBIDDEN|Http::STATUS_NOT_FOUND|Http::STATUS_METHOD_NOT_ALLOWED, array<empty>, array{}>
+	 * @return DataResponse<Http::STATUS_OK|Http::STATUS_ACCEPTED, TalkChatMessageWithParent, array{X-Chat-Last-Common-Read?: numeric-string}>|DataResponse<Http::STATUS_BAD_REQUEST, array{error: string}, array{}>|DataResponse<Http::STATUS_FORBIDDEN|Http::STATUS_NOT_FOUND|Http::STATUS_METHOD_NOT_ALLOWED, array<empty>, array{}>
 	 *
 	 * 200: Message edited successfully
 	 * 202: Message edited successfully, but Matterbridge is configured, so the information can be replicated elsewhere
-	 * 400: Editing message is not possible
+	 * 400: Editing message is not possible, e.g. when the new message is empty or the message is too old
 	 * 403: Missing permissions to edit message
 	 * 404: Message not found
 	 * 405: Editing this message type is not allowed
@@ -797,16 +797,23 @@ public function editMessage(int $messageId, string $message): DataResponse {
 		$maxAge->sub(new \DateInterval('P1D'));
 		if ($comment->getCreationDateTime() < $maxAge) {
 			// Message is too old
-			return new DataResponse([], Http::STATUS_BAD_REQUEST);
+			return new DataResponse(['error' => 'age'], Http::STATUS_BAD_REQUEST);
 		}
 
-		$systemMessageComment = $this->chatManager->editMessage(
-			$this->room,
-			$comment,
-			$this->participant,
-			$this->timeFactory->getDateTime(),
-			$message
-		);
+		try {
+			$systemMessageComment = $this->chatManager->editMessage(
+				$this->room,
+				$comment,
+				$this->participant,
+				$this->timeFactory->getDateTime(),
+				$message
+			);
+		} catch (\InvalidArgumentException $e) {
+			if ($e->getMessage() === 'object_share') {
+				return new DataResponse([], Http::STATUS_METHOD_NOT_ALLOWED);
+			}
+			return new DataResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
 
 		$systemMessage = $this->messageParser->createMessage($this->room, $this->participant, $systemMessageComment, $this->l);
 		$this->messageParser->parseMessage($systemMessage);
diff --git a/openapi.json b/openapi.json
index 0beca30fc4f..c0ea7e43062 100644
--- a/openapi.json
+++ b/openapi.json
@@ -6282,7 +6282,7 @@
                         }
                     },
                     "400": {
-                        "description": "Editing message is not possible",
+                        "description": "Editing message is not possible, e.g. when the new message is empty or the message is too old",
                         "content": {
                             "application/json": {
                                 "schema": {
@@ -6301,7 +6301,17 @@
                                                 "meta": {
                                                     "$ref": "#/components/schemas/OCSMeta"
                                                 },
-                                                "data": {}
+                                                "data": {
+                                                    "type": "object",
+                                                    "required": [
+                                                        "error"
+                                                    ],
+                                                    "properties": {
+                                                        "error": {
+                                                            "type": "string"
+                                                        }
+                                                    }
+                                                }
                                             }
                                         }
                                     }
diff --git a/tests/integration/features/chat-1/edit-message.feature b/tests/integration/features/chat-1/edit-message.feature
index 9d6e25f1169..4af56cd0908 100644
--- a/tests/integration/features/chat-1/edit-message.feature
+++ b/tests/integration/features/chat-1/edit-message.feature
@@ -50,3 +50,25 @@ Feature: chat-1/edit-message
     Then user "participant2" sees the following messages in room "room" with 200
       | room | actorType | actorId      | actorDisplayName         | message            | messageParameters | parentMessage |
       | room | users     | participant2 | participant2-displayname | Message 1 - Edit 2 | []                |               |
+    And user "participant2" edits message "Message 1 - Edit 1" in room "room" to "" with 400
+    Then user "participant1" sees the following messages in room "room" with 200
+      | room | actorType | actorId      | actorDisplayName         | message            | messageParameters | parentMessage |
+      | room | users     | participant2 | participant2-displayname | Message 1 - Edit 2 | []                |               |
+
+  Scenario: Editing a caption
+    Given user "participant1" creates room "room" (v4)
+      | roomType | 3 |
+      | roomName | room |
+    And user "participant1" shares "welcome.txt" with room "room"
+      | talkMetaData | {"caption":"Caption 1"} |
+    And user "participant1" sees the following messages in room "room" with 200
+      | room | actorType | actorId      | actorDisplayName         | message  | messageParameters |
+      | room | users     | participant1 | participant1-displayname | Caption 1 | "IGNORE"          |
+    When user "participant1" edits message "Caption 1" in room "room" to "Caption 1 - Edit 1" with 200
+    Then user "participant1" sees the following messages in room "room" with 200
+      | room | actorType | actorId      | actorDisplayName         | message            | messageParameters |
+      | room | users     | participant1 | participant1-displayname | Caption 1 - Edit 1 | "IGNORE"          |
+    When user "participant1" edits message "Caption 1" in room "room" to "" with 400
+    Then user "participant1" sees the following messages in room "room" with 200
+      | room | actorType | actorId      | actorDisplayName         | message            | messageParameters |
+      | room | users     | participant1 | participant1-displayname | Caption 1 - Edit 1 | "IGNORE"          |