diff --git a/core/themes/bartik/bartik.theme b/core/themes/bartik/bartik.theme
index e4f03b9..a4222bd 100644
--- a/core/themes/bartik/bartik.theme
+++ b/core/themes/bartik/bartik.theme
@@ -83,7 +83,7 @@ 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');
+  drupal_add_library('bartik', 'maintenance_page');
   $variables['styles'] = drupal_get_css();
 
   $site_config = config('system.site');
@@ -102,6 +102,24 @@ function bartik_preprocess_maintenance_page(&$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) {