diff --git a/core/modules/rest/src/RequestHandler.php b/core/modules/rest/src/RequestHandler.php
index d3b69b5..ee4b890 100644
--- a/core/modules/rest/src/RequestHandler.php
+++ b/core/modules/rest/src/RequestHandler.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\rest;
 
-use Drupal\Core\Cache\CacheableResponse;
 use Drupal\Core\Render\RenderContext;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Symfony\Component\DependencyInjection\ContainerAwareInterface;
@@ -68,7 +67,7 @@ public function handle(RouteMatchInterface $route_match, Request $request) {
         catch (UnexpectedValueException $e) {
           $error['error'] = $e->getMessage();
           $content = $serializer->serialize($error, $format);
-          return new Response($content, 400, ['Content-Type' => $request->getMimeType($format)]);
+          return new Response($content, 400, array('Content-Type' => $request->getMimeType($format)));
         }
       }
       else {