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 +9,13 @@
 import { pluralizeAndTrim } from '../utils/text-utils';
 
 function useInlineSidebarText(
-  threadInfo: ThreadInfo,
+  threadInfo: ?ThreadInfo,
 ): {
   sendersText: string,
   repliesText: string,
 } {
-  const repliesCount = threadInfo.repliesCount || 1;
-  const repliesText = `${repliesCount} ${
-    repliesCount > 1 ? 'replies' : 'reply'
-  }`;
-
   const threadMembers = useSelector(
-    relativeMemberInfoSelectorForMembersOfThread(threadInfo.id),
+    relativeMemberInfoSelectorForMembersOfThread(threadInfo?.id),
   );
   const sendersText = React.useMemo(() => {
     const senders = threadMembers
@@ -29,13 +24,22 @@
     return senders.length > 0 ? `${pluralizeAndTrim(senders, 25)} sent ` : '';
   }, [threadMembers]);
 
-  return React.useMemo(
-    () => ({
+  const noThreadInfo = !threadInfo;
+
+  return React.useMemo(() => {
+    if (noThreadInfo) {
+      return { sendersText: '', repliesText: '' };
+    }
+    const repliesCount = threadInfo?.repliesCount || 1;
+    const repliesText = `${repliesCount} ${
+      repliesCount > 1 ? 'replies' : 'reply'
+    }`;
+
+    return {
       sendersText,
       repliesText,
-    }),
-    [sendersText, repliesText],
-  );
+    };
+  }, [noThreadInfo, sendersText, threadInfo?.repliesCount]);
 }
 
 export default useInlineSidebarText;