diff --git c/core/modules/system/lib/Drupal/system/Controller/ThemeController.php w/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
index aa9a6be..6f2a1ac 100644
--- c/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
+++ w/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
@@ -8,16 +8,17 @@
 namespace Drupal\system\Controller;
 
 use Drupal\Core\Controller\ControllerBase;
-use Symfony\Component\DependencyInjection\ContainerInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
 use Drupal\Core\Config\ConfigFactory;
 use Drupal\Core\Access\CsrfTokenGenerator;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 
 /**
  * Controller for theme handling.
  */
-class ThemeController extends ControllerBase {
+class ThemeController extends ControllerBase implements ContainerInjectionInterface {
 
   /**
    * The config factory service.