diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -1852,6 +1852,7 @@
   ]);
 }
 
+// eslint-disable-next-line no-unused-vars
 function useChatMentionSearchIndex(): {
   +[id: string]: SentencePrefixSearchIndex,
 } {
@@ -1880,20 +1881,12 @@
   }, [chatMentionCandidatesObj]);
 }
 
+const emptySearchIndex = new SentencePrefixSearchIndex();
 function useThreadChatMentionSearchIndex(
+  // eslint-disable-next-line no-unused-vars
   threadInfo: ThreadInfo,
 ): SentencePrefixSearchIndex {
-  const chatMentionCandidatesSearchIndex = useChatMentionSearchIndex();
-  const { communityThreadIDForGenesisThreads } =
-    useChatMentionCandidatesObjAndUtils();
-  if (threadInfo.community === genesis.id) {
-    return chatMentionCandidatesSearchIndex[
-      communityThreadIDForGenesisThreads[threadInfo.id]
-    ];
-  }
-  return chatMentionCandidatesSearchIndex[
-    threadInfo.community ?? threadInfo.id
-  ];
+  return emptySearchIndex;
 }
 
 export {