diff --git a/backend/src/plugins/Post/util/postMessage.ts b/backend/src/plugins/Post/util/postMessage.ts
index e45bfb24..199b0ead 100644
--- a/backend/src/plugins/Post/util/postMessage.ts
+++ b/backend/src/plugins/Post/util/postMessage.ts
@@ -47,6 +47,7 @@ export async function postMessage(
       }
     }
 
+    content.allowedMentions = content.allowedMentions || {};
     content.allowedMentions.everyone = false;
   }