diff --git a/core/modules/system/src/Tests/Menu/MenuRouterTest.php b/core/modules/system/src/Tests/Menu/MenuRouterTest.php
index 202c662..4383658 100644
--- a/core/modules/system/src/Tests/Menu/MenuRouterTest.php
+++ b/core/modules/system/src/Tests/Menu/MenuRouterTest.php
@@ -342,6 +342,8 @@ public function testMaintenanceModeLoginPaths() {
     $offline_message = t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => \Drupal::config('system.site')->get('name')));
     $this->drupalGet('test-page');
     $this->assertText($offline_message);
+    $this->drupalGet('menu_login_callback');
+    $this->assertText('This is TestControllers::testLogin.', 'Maintenance mode can be bypassed using an event subscriber.');
 
     $this->container->get('state')->set('system.maintenance_mode', FALSE);
   }
diff --git a/core/modules/system/tests/modules/menu_test/menu_test.routing.yml b/core/modules/system/tests/modules/menu_test/menu_test.routing.yml
index 724e58f..6c3c106 100644
--- a/core/modules/system/tests/modules/menu_test/menu_test.routing.yml
+++ b/core/modules/system/tests/modules/menu_test/menu_test.routing.yml
@@ -14,6 +14,13 @@ menu_test.menu_callback_title:
   requirements:
     _access: 'TRUE'
 
+menu_test.login_callback:
+  path: '/menu_login_callback'
+  defaults:
+    _content: '\Drupal\menu_test\TestControllers::testLogin'
+  requirements:
+    _access: 'TRUE'
+
 menu_test.callback_description:
   path: '/menu_callback_description'
   defaults:
diff --git a/core/modules/system/tests/modules/menu_test/menu_test.services.yml b/core/modules/system/tests/modules/menu_test/menu_test.services.yml
index 8841320..951274f 100644
--- a/core/modules/system/tests/modules/menu_test/menu_test.services.yml
+++ b/core/modules/system/tests/modules/menu_test/menu_test.services.yml
@@ -1,4 +1,9 @@
 services:
+  menu_test_maintenance_mode_exemption:
+    class: Drupal\menu_test\Site\MaintenanceExemption
+    tags:
+      - { name: maintenance_mode_exemption }
+
   theme.negotiator.test_theme:
     class: Drupal\menu_test\Theme\TestThemeNegotiator
     tags:
diff --git a/core/modules/system/tests/modules/menu_test/src/Site/MaintenanceExemption.php b/core/modules/system/tests/modules/menu_test/src/Site/MaintenanceExemption.php
new file mode 100644
index 0000000..750a83a
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_test/src/Site/MaintenanceExemption.php
@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\menu_test\Site\MaintenanceExemption.
+ */
+
+namespace Drupal\menu_test\Site;
+
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Site\MaintenanceExemptionInterface;
+
+
+/**
+ * Maintenance mode subscriber to set site online on a test.
+ */
+class MaintenanceExemption implements MaintenanceExemptionInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function exempt(RouteMatchInterface $route_match, AccountInterface $account) {
+    if ($route_match->getRouteName() == 'menu_test.login_callback') {
+      return TRUE;
+    }
+  }
+
+}
diff --git a/core/modules/system/tests/modules/menu_test/src/TestControllers.php b/core/modules/system/tests/modules/menu_test/src/TestControllers.php
index df3f090..608e0c7 100644
--- a/core/modules/system/tests/modules/menu_test/src/TestControllers.php
+++ b/core/modules/system/tests/modules/menu_test/src/TestControllers.php
@@ -16,6 +16,13 @@
 class TestControllers {
 
   /**
+   * Returns page to be used as a login path.
+   */
+  public function testLogin() {
+    return 'This is TestControllers::testLogin.';
+  }
+
+  /**
    * Prints out test data.
    */
   public function test1() {