diff --git a/src/pages/home/tsx/login_handler/FirebaseLoginHandler.tsx b/src/pages/home/tsx/login_handler/FirebaseLoginHandler.tsx
index c341a39..2b683b6 100644
--- a/src/pages/home/tsx/login_handler/FirebaseLoginHandler.tsx
+++ b/src/pages/home/tsx/login_handler/FirebaseLoginHandler.tsx
@@ -30,7 +30,7 @@ export class FirebaseLoginHandler extends LoginHandler {
 
     public listRooms(resultCallback) {
         if (this.uid === undefined) {
-            return; // TODO(binit): throw an exception? reject a promise?
+            throw new Error("FirebaseLoginHandler.listRooms(): this.uid is null");
         }
 
         onValue(ref(this.db, 'rooms/' + this.uid + '/robots'), (snapshot) => {