diff --git a/web/src/stream_events.ts b/web/src/stream_events.ts
index d9983ccb5f..6282b09347 100644
--- a/web/src/stream_events.ts
+++ b/web/src/stream_events.ts
@@ -247,11 +247,8 @@ export function mark_subscribed(
     user_profile.update_user_profile_streams_list_for_users([people.my_current_user_id()]);
 }
 
-export function mark_unsubscribed(sub: StreamSubscription | undefined): void {
-    if (sub === undefined) {
-        // We don't know about this stream
-        return;
-    } else if (sub.subscribed) {
+export function mark_unsubscribed(sub: StreamSubscription): void {
+    if (sub.subscribed) {
         stream_data.unsubscribe_myself(sub);
         if (overlays.streams_open()) {
             stream_settings_ui.update_settings_for_unsubscribed(sub);
diff --git a/web/tests/stream_events.test.cjs b/web/tests/stream_events.test.cjs
index 2eba30cc97..e8d5a0fb28 100644
--- a/web/tests/stream_events.test.cjs
+++ b/web/tests/stream_events.test.cjs
@@ -277,11 +277,6 @@ test("update_property", ({override}) => {
     }
 });
 
-test("marked_unsubscribed (code coverage)", () => {
-    // We don't error for unsubscribed streams for some reason.
-    stream_events.mark_unsubscribed(undefined);
-});
-
 test("marked_(un)subscribed (early return)", () => {
     // The early-return prevents us from exploding or needing
     // to override functions with side effects