diff --git a/lib/shared/ancestor-threads.js b/lib/shared/ancestor-threads.js
--- a/lib/shared/ancestor-threads.js
+++ b/lib/shared/ancestor-threads.js
@@ -1,5 +1,7 @@
 // @flow
 
+import * as React from 'react';
+
 import genesis from '../facts/genesis.js';
 import {
   threadInfoSelector,
@@ -12,18 +14,20 @@
 function useAncestorThreads(
   threadInfo: ThreadInfo,
 ): $ReadOnlyArray<ThreadInfo> {
-  return useSelector(state => {
-    if (!threadIsPending(threadInfo.id)) {
-      const ancestorThreads = ancestorThreadInfos(threadInfo.id)(state);
-      if (ancestorThreads.length > 1) {
-        return ancestorThreads.slice(0, -1);
-      }
+  const ancestorThreads = useSelector(ancestorThreadInfos(threadInfo.id));
 
-      return ancestorThreads;
+  const genesisThreadInfo = useSelector(
+    state => threadInfoSelector(state)[genesis.id],
+  );
+
+  return React.useMemo(() => {
+    if (!threadIsPending(threadInfo.id)) {
+      return ancestorThreads.length > 1
+        ? ancestorThreads.slice(0, -1)
+        : ancestorThreads;
     }
-    const genesisThreadInfo = threadInfoSelector(state)[genesis.id];
     return genesisThreadInfo ? [genesisThreadInfo] : [];
-  });
+  }, [ancestorThreads, genesisThreadInfo, threadInfo.id]);
 }
 
 export { useAncestorThreads };