--- a/src/Plugin/views/sort/NullSort.php
+++ b/src/Plugin/views/sort/NullSort.php
@@ -51,8 +51,8 @@
       default:
         return $this->t('NULL last');

-      case 'DESC';
-      case 'desc';
+      case 'DESC':
+      case 'desc':
         return $this->t('NULL first');
     }
   }