diff --git a/src/server/api/endpoints/i/read-all-messaging-messages.ts b/src/server/api/endpoints/i/read-all-messaging-messages.ts
index 036ec02d6..e47ef16bd 100644
--- a/src/server/api/endpoints/i/read-all-messaging-messages.ts
+++ b/src/server/api/endpoints/i/read-all-messaging-messages.ts
@@ -1,6 +1,6 @@
 import { publishMainStream } from '../../../../services/stream';
 import define from '../../define';
-import { MessagingMessages } from '../../../../models';
+import { MessagingMessages, UserGroupJoinings } from '../../../../models';
 
 export const meta = {
 	desc: {
@@ -27,5 +27,16 @@ export default define(meta, async (ps, user) => {
 		isRead: true
 	});
 
+	const joinings = await UserGroupJoinings.find({ userId: user.id });
+
+	await Promise.all(joinings.map(j => MessagingMessages.createQueryBuilder().update()
+		.set({
+			reads: (() => `array_append("reads", '${user.id}')`) as any
+		})
+		.where(`groupId = :groupId`, { groupId: j.userGroupId })
+		.andWhere('userId != :userId', { userId: user.id })
+		.andWhere('NOT (:userId = ANY(reads))', { userId: user.id })
+		.execute()));
+
 	publishMainStream(user.id, 'readAllMessagingMessages');
 });