diff --git a/core/themes/bartik/bartik.theme b/core/themes/bartik/bartik.theme
index ed59e8d..952e259 100644
--- a/core/themes/bartik/bartik.theme
+++ b/core/themes/bartik/bartik.theme
@@ -84,8 +84,16 @@ function bartik_preprocess_maintenance_page(&$variables) {
   if (!$variables['db_is_active']) {
     $variables['site_name'] = '';
   }
-  drupal_add_css(drupal_get_path('theme', 'bartik') . '/css/maintenance-page.css');
   $variables['styles'] = drupal_get_css();
+  $libraries = array(
+    '#attached' => array(
+      'library' => array(
+        array('bartik', 'maintenance_page'),
+      ),
+    ),
+  );
+
+  drupal_render($libraries);
 
   $site_config = Drupal::config('system.site');
   // Always print the site name and slogan, but if they are toggled off, we'll
@@ -103,6 +111,24 @@ function bartik_preprocess_maintenance_page(&$variables) {
 }
 
 /**
+ * Implements hook_library_info().
+ */
+function bartik_library_info() {
+  $path = drupal_get_path('theme', 'bartik');
+
+  $libraries['maintenance_page'] = array(
+    'version' => VERSION,
+    'css' => array(
+      $path . '/css/maintenance-page.css' => array(
+        'group' => CSS_AGGREGATE_THEME,
+      ),
+    ),
+  );
+
+  return $libraries;
+}
+
+/**
  * Implements hook_preprocess_HOOK() for node.html.twig.
  */
 function bartik_preprocess_node(&$variables) {