diff --git a/api/activitypub/sendNote.ts b/api/activitypub/sendNote.ts
index 280ee5a59faed402ec2957eaed2e14a9fbdb4909..66a5423be512d9a0d96d0966e5d1708b6d6c78f9 100644
--- a/api/activitypub/sendNote.ts
+++ b/api/activitypub/sendNote.ts
@@ -103,7 +103,7 @@ export default async function (req: VercelRequest, res: VercelResponse) {
     }
   }
 
-  if( sentIds.size > 0 ) {
+  if( sentIds.length > 0 ) {
     sendingIds.add(...sentIds);
   }
   const newSentIds = [];