diff -u b/core/modules/filter/lib/Drupal/filter/FilterFormatListController.php b/core/modules/filter/lib/Drupal/filter/FilterFormatListController.php
--- b/core/modules/filter/lib/Drupal/filter/FilterFormatListController.php
+++ b/core/modules/filter/lib/Drupal/filter/FilterFormatListController.php
@@ -134,6 +134,8 @@
     if ($entity->isFallbackFormat()) {
       unset($operations['disable']);
     }
+
+    return $operations;
   }
 
   /**