diff --git a/core/core.services.yml b/core/core.services.yml
index fa5c33e..e5fae05 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -611,7 +611,7 @@ services:
       - { name: service_collector, tag: maintenance_mode_exemption, call: addExemption }
   maintenance_mode_subscriber:
     class: Drupal\Core\EventSubscriber\MaintenanceModeSubscriber
-    arguments: ['@site_status_negotiator', '@config.factory', '@string_translation', '@url_generator', '@current_user']
+    arguments: ['@site_status_negotiator', '@string_translation', '@url_generator', '@current_user']
     tags:
       - { name: event_subscriber }
   path_subscriber:
diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index 320cb06..7183019 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -18,6 +18,7 @@
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Drupal\Component\Utility\String;
+use Drupal\Component\Utility\Xss;
 use Symfony\Component\Debug\Exception\FlattenException;
 use Drupal\Core\ContentNegotiation;
 use Drupal\Core\Utility\Error;
@@ -324,6 +325,29 @@ public function on500Html(FlattenException $exception, Request $request) {
   }
 
   /**
+   * Deliver the 503 page if the site is in maintenance mode.
+   *
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
+   *   The flattened exception.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object.
+   */
+  public function on503Html(FlattenException $exception, Request $request) {
+    $maintenance_message = $this->container->get('config.factory')->get('system.maintenance')->get('message');
+    $site_name = $this->container->get('config.factory')->get('system.site')->get('name');
+
+    $content = Xss::filterAdmin(String::format($maintenance_message, array('@site' => $site_name)));
+    $output = DefaultHtmlPageRenderer::renderPage($content, $this->t('Site under maintenance'));
+    $response = new Response($output);
+    $response->setStatusCode(503, 'Service Unavailable');
+
+    return $response;
+  }
+
+  /**
    * Processes an AccessDenied exception that occurred on a JSON request.
    *
    * @param \Symfony\Component\Debug\Exception\FlattenException $exception
diff --git a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
index b36ec07..fe595b1 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
@@ -7,21 +7,17 @@
 
 namespace Drupal\Core\EventSubscriber;
 
-use Drupal\Component\Utility\String;
-use Drupal\Component\Utility\Xss;
-use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Core\Page\DefaultHtmlPageRenderer;
 use Drupal\Core\Routing\RouteMatch;
 use Drupal\Core\Routing\UrlGeneratorInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Site\StatusNegotiatorInterface;
-use Drupal\Core\State\StateInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
-use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\HttpKernel\KernelEvents;
 
 /**
@@ -46,13 +42,6 @@ class MaintenanceModeSubscriber implements EventSubscriberInterface {
   protected $account;
 
   /**
-   * The config factory.
-   *
-   * @var \Drupal\Core\Config\ConfigFactoryInterface
-   */
-  protected $config;
-
-  /**
    * The url generator.
    *
    * @var \Drupal\Core\Routing\UrlGeneratorInterface
@@ -64,8 +53,6 @@ class MaintenanceModeSubscriber implements EventSubscriberInterface {
    *
    * @param \Drupal\Core\Site\StatusNegotiatorInterface $status_negotiator
    *   The site status negotiator.
-   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
-   *   The config factory.
    * @param \Drupal\Core\StringTranslation\TranslationInterface $translation
    *   The string translation.
    * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
@@ -73,9 +60,8 @@ class MaintenanceModeSubscriber implements EventSubscriberInterface {
    * @param \Drupal\Core\Session\AccountInterface $account
    *   The current user.
    */
-  public function __construct(StatusNegotiatorInterface $status_negotiator, ConfigFactoryInterface $config_factory, TranslationInterface $translation, UrlGeneratorInterface $url_generator, AccountInterface $account) {
+  public function __construct(StatusNegotiatorInterface $status_negotiator, TranslationInterface $translation, UrlGeneratorInterface $url_generator, AccountInterface $account) {
     $this->statusNegotiator = $status_negotiator;
-    $this->config = $config_factory;
     $this->stringTranslation = $translation;
     $this->urlGenerator = $url_generator;
     $this->account = $account;
@@ -88,19 +74,12 @@ public function __construct(StatusNegotiatorInterface $status_negotiator, Config
    *   The event to process.
    */
   public function onKernelRequestMaintenance(GetResponseEvent $event) {
-    if ($this->statusNegotiator->getStatus() != StatusNegotiatorInterface::SITE_ONLINE) {
+    if ($event->getRequestType() == HttpKernelInterface::MASTER_REQUEST && $this->statusNegotiator->getStatus() != StatusNegotiatorInterface::SITE_ONLINE) {
       $route_match = RouteMatch::createFromRequest($event->getRequest());
       if (!$this->statusNegotiator->exempt($route_match, $this->account)) {
         // Deliver the 503 page if the site is in maintenance mode and the
         // logged in user is not allowed to bypass it.
-        drupal_maintenance_theme();
-        $content = Xss::filterAdmin(String::format($this->config->get('system.maintenance')->get('message'), array(
-          '@site' => $this->config->get('system.site')->get('name'),
-        )));
-        $content = DefaultHtmlPageRenderer::renderPage($content, $this->t('Site under maintenance'));
-        $response = new Response('Service unavailable', 503);
-        $response->setContent($content);
-        $event->setResponse($response);
+        throw new ServiceUnavailableHttpException();
       }
       else {
         // Display a message if the logged in user has access to the site in
diff --git a/core/modules/user/src/Site/MaintenanceExemption.php b/core/modules/user/src/Site/MaintenanceExemption.php
index c914c4d..6e3ab4b 100644
--- a/core/modules/user/src/Site/MaintenanceExemption.php
+++ b/core/modules/user/src/Site/MaintenanceExemption.php
@@ -21,9 +21,7 @@ class MaintenanceExemption implements MaintenanceExemptionInterface {
    */
   public function exempt(RouteMatchInterface $route_match, AccountInterface $account) {
     $route_name = $route_match->getRouteName();
-    if ($route_name == 'user.login' || $route_name == 'user.pass' || $route_name == 'user.reset') {
-      return TRUE;
-    }
+    return in_array($route_name, ['user.login', 'user.pass', 'user.reset']);
   }
 
 }