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
@@ -9,18 +9,18 @@
 import { pluralizeAndTrim } from '../utils/text-utils';
 
 function useInlineSidebarText(
-  threadInfo: ThreadInfo,
+  threadInfo: ?ThreadInfo,
 ): {
   sendersText: string,
   repliesText: string,
 } {
-  const repliesCount = threadInfo.repliesCount || 1;
+  const repliesCount = threadInfo?.repliesCount || 1;
   const repliesText = `${repliesCount} ${
     repliesCount > 1 ? 'replies' : 'reply'
   }`;
 
   const threadMembers = useSelector(
-    relativeMemberInfoSelectorForMembersOfThread(threadInfo.id),
+    relativeMemberInfoSelectorForMembersOfThread(threadInfo?.id),
   );
   const sendersText = React.useMemo(() => {
     const senders = threadMembers
@@ -29,13 +29,15 @@
     return senders.length > 0 ? `${pluralizeAndTrim(senders, 25)} sent ` : '';
   }, [threadMembers]);
 
-  return React.useMemo(
-    () => ({
+  return React.useMemo(() => {
+    if (!threadInfo) {
+      return { sendersText: '', repliesText: '' };
+    }
+    return {
       sendersText,
       repliesText,
-    }),
-    [sendersText, repliesText],
-  );
+    };
+  }, [threadInfo, sendersText, repliesText]);
 }
 
 export default useInlineSidebarText;