diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 7613e23..c65ba3b 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2417,8 +2417,6 @@ function template_preprocess_maintenance_page(&$variables) {
   // These are usually added from system_page_build() except maintenance.css.
   // When the database is inactive it's not called so we add it here.
   $default_css['library'][] = array('core', 'normalize');
-  $default_css['library'][] = array('system', 'base');
-  $default_css['library'][] = array('system', 'admin');
   $default_css['library'][] = array('system', 'maintenance');
   $attached = array('#attached' => $default_css);
   drupal_render($attached);
diff --git a/core/modules/block/block.libraries.yml b/core/modules/block/block.libraries.yml
index 20a5ce9..e0ef44c 100644
--- a/core/modules/block/block.libraries.yml
+++ b/core/modules/block/block.libraries.yml
@@ -16,3 +16,4 @@ drupal.block.admin:
   dependencies:
     - core/jquery
     - core/drupal
+    - core/drupal.ajax
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
index 4b22a29..56b8aee 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/RenderElementTypesTest.php
@@ -12,12 +12,20 @@
 use Drupal\Component\Utility\Xss;
 use Drupal\Core\Language\Language;
 use Drupal\Core\Template\Attribute;
-use Drupal\simpletest\WebTestBase;
+use Drupal\simpletest\DrupalUnitTestBase;
 
 /**
  * Tests the markup of core render element types passed to drupal_render().
  */
-class RenderElementTypesTest extends WebTestBase {
+class RenderElementTypesTest extends DrupalUnitTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system');
+
   public static function getInfo() {
     return array(
       'name' => 'Render element types',
@@ -26,6 +34,12 @@ public static function getInfo() {
     );
   }
 
+  protected function setUp() {
+    parent::setUp();
+    $this->installConfig(array('system'));
+    $this->container->get('theme_handler')->enable(array('stark'));
+  }
+
   /**
    * Asserts that an array of elements is rendered properly.
    *
@@ -173,11 +187,9 @@ function testMaintenancePage() {
     $path = drupal_get_path('module', 'system');
     $default_css = array(
       '#attached' => array(
-        'css' => array(
-          $path . '/css/system.module.css',
-          $path . '/css/system.admin.css',
-          $path . '/css/system.maintenance.css',
-          $path . '/css/system.theme.css',
+        'library' => array(
+          array('core', 'normalize'),
+          array('system', 'maintenance'),
         ),
       ),
     );
@@ -230,7 +242,7 @@ function testMaintenancePage() {
     );
 
     // We have to reset drupal_add_css between each test.
-    drupal_static_reset('_drupal_add_css');
+    drupal_static_reset();
 
     // Test basic string for maintenance page content.
     $elements = array(
@@ -248,7 +260,7 @@ function testMaintenancePage() {
     $this->assertElements($elements);
 
     // Test render array for maintenance page content.
-    drupal_static_reset('_drupal_add_css');
+    drupal_static_reset();
     $elements[0]['name'] = "#theme 'maintenance_page' with content as a render array";
     $elements[0]['value']['#content'] = array('#markup' => '<span>foo</span>');
     $this->assertElements($elements);