diff --git a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
index 58c678b..3f4b207 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
@@ -28,13 +28,15 @@ protected static function getPriority() {
   }
 
   /**
-   * Handles all 4XYs errors for JSON.
+   * Handles all 400 errors for JSON.
    *
    * @param \Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent $event
    *   The event to process.
    */
-  public function on4XY(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse(array('message' => $event->getException()->getMessage()), Response::HTTP_FORBIDDEN);
+  public function on400(GetResponseForExceptionEvent $event) {
+    /** @var \Symfony\Component\HttpKernel\Exception\HttpExceptionInterface $exception */
+    $exception = $event->getException();
+    $response = new JsonResponse(array('message' => $event->getException()->getMessage()), $exception->getStatusCode());
     $event->setResponse($response);
   }
 
diff --git a/core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php b/core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php
index a9e022f..6d4555d 100644
--- a/core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php
+++ b/core/lib/Drupal/Core/EventSubscriber/HttpExceptionSubscriberBase.php
@@ -90,7 +90,9 @@ public function onException(GetResponseForExceptionEvent $event) {
 
     if ($exception instanceof HttpExceptionInterface && (empty($handled_formats) || in_array($format, $handled_formats))) {
       $method = 'on' . $exception->getStatusCode();
-      $method_fallback = 'on' . (string) (int) ($exception->getStatusCode() / 100) . 'XY';
+      // Keep just the leading number of the status code to produce either a
+      // on400 or a 500 method callback.
+      $method_fallback = 'on' . (int) ($exception->getStatusCode() / 100) . '00';
       // We want to allow the method to be called and still not set a response
       // if it has additional filtering logic to determine when it will apply.
       // It is therefore the method's responsibility to set the response on the