diff --git a/core/modules/system/tests/modules/design_test/lib/Drupal/design_test/Controller/DesignTestController.php b/core/modules/system/tests/modules/design_test/lib/Drupal/design_test/Controller/DesignTestController.php
index 4a099b4..34ef64f 100644
--- a/core/modules/system/tests/modules/design_test/lib/Drupal/design_test/Controller/DesignTestController.php
+++ b/core/modules/system/tests/modules/design_test/lib/Drupal/design_test/Controller/DesignTestController.php
@@ -55,8 +55,7 @@ public function categoryPage($category) {
         $data['link']['hidden'] = 0;
       }
     }
-    $build = menu_tree_output($tree);
-    return $build;
+    return menu_tree_output($tree);
   }
 
 }