diff --git a/core/modules/image/lib/Drupal/image/Controller/ImageStyleDownloadController.php b/core/modules/image/lib/Drupal/image/Controller/ImageStyleDownloadController.php
index 2647bae..1d65270 100644
--- a/core/modules/image/lib/Drupal/image/Controller/ImageStyleDownloadController.php
+++ b/core/modules/image/lib/Drupal/image/Controller/ImageStyleDownloadController.php
@@ -19,6 +19,7 @@
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
 
 /**
  * Defines a controller to serve image styles.