diff --git a/lib/hooks/inline-sidebar-text.react.js b/lib/hooks/inline-sidebar-text.react.js
--- a/lib/hooks/inline-sidebar-text.react.js
+++ b/lib/hooks/inline-sidebar-text.react.js
@@ -14,7 +14,7 @@
   sendersText: string,
   repliesText: string,
 } {
-  const repliesCount = threadInfo.repliesCount || 1;
+  const repliesCount = threadInfo?.repliesCount ?? 1;
   const repliesText = `${repliesCount} ${
     repliesCount > 1 ? 'replies' : 'reply'
   }`;
@@ -29,7 +29,13 @@
     return senders.length > 0 ? `${pluralizeAndTrim(senders, 25)} sent ` : '';
   }, [threadMembers]);
 
-  return { sendersText, repliesText };
+  return React.useMemo(
+    () => ({
+      sendersText,
+      repliesText,
+    }),
+    [sendersText, repliesText],
+  );
 }
 
 export default useInlineSidebarText;