diff --git a/keyserver/src/deleters/thread-deleters.js b/keyserver/src/deleters/thread-deleters.js
--- a/keyserver/src/deleters/thread-deleters.js
+++ b/keyserver/src/deleters/thread-deleters.js
@@ -54,7 +54,7 @@
   const threadIDs = await fetchContainedThreadIDs(threadID);
 
   const [{ threadInfos: serverThreadInfos }] = await Promise.all([
-    fetchServerThreadInfos({ threadIDs: new Set(threadID) }),
+    fetchServerThreadInfos({ threadIDs: new Set(threadIDs) }),
     rescindPushNotifs(
       SQL`n.thread IN (${threadIDs})`,
       SQL`IF(m.thread IN (${threadIDs}), NULL, m.thread)`,