diff --git a/web/src/narrow_state.ts b/web/src/narrow_state.ts
index e2c9023e21..0bf42677b6 100644
--- a/web/src/narrow_state.ts
+++ b/web/src/narrow_state.ts
@@ -299,6 +299,7 @@ export function _possible_unread_message_ids(
             return [];
         }
         if (sub === undefined || topic_name === undefined) {
+            /* istanbul ignore next */
             return [];
         }
         return unread.get_msg_ids_for_topic(sub.stream_id, topic_name);