diff --git a/api/activitypub/sendNote.ts b/api/activitypub/sendNote.ts
index c338152208b7a29414472ba5f518a5d246d19d7a..93b659521d75e53a3e202cd62528bd348d076490 100644
--- a/api/activitypub/sendNote.ts
+++ b/api/activitypub/sendNote.ts
@@ -96,7 +96,7 @@ export default async function (req: VercelRequest, res: VercelResponse) {
           const response = await sendSignedRequest(actorInbox, <AP.Activity> item);
           console.log(`Send result: ${actorInbox}`, response.status, response.statusText, await response.text());
 
-          sendingIds.push(item.id)
+          sendingIds.add(item.id)
         }
       }
     } catch (ex) {