diff --git a/api/activitypub/sendNote.ts b/api/activitypub/sendNote.ts
index 5ce73ebd5bb41d50a571b275113c2299d5663f14..c338152208b7a29414472ba5f518a5d246d19d7a 100644
--- a/api/activitypub/sendNote.ts
+++ b/api/activitypub/sendNote.ts
@@ -66,7 +66,7 @@ export default async function (req: VercelRequest, res: VercelResponse) {
   const followersCollection = db.collection('followers');
   const followersQuerySnapshot = await followersCollection.get();
 
-  let sendingIds = Set();
+  let sendingIds = new Set();
 
   for (const followerDoc of followersQuerySnapshot.docs) {
     const follower = followerDoc.data();