diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 87b3b18..61f5b2f 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2836,11 +2836,8 @@ function theme_get_suggestions($args, $base, $delimiter = '__') {
  *   - content - An array of page content.
  */
 function template_preprocess_maintenance_page(&$variables) {
-  global $theme;
   $language_interface = language(Language::TYPE_INTERFACE);
-  // Retrieve the theme data to list all available regions.
-  $theme_data = list_themes();
-  $regions = $theme_data[$theme]->info['regions'];
+  $site_config = Drupal::config('system.site');
 
   // Add favicon
   if (theme_get_setting('features.favicon')) {
@@ -2849,11 +2846,14 @@ function template_preprocess_maintenance_page(&$variables) {
     drupal_add_html_head_link(array('rel' => 'shortcut icon', 'href' => drupal_strip_dangerous_protocols($favicon), 'type' => $type));
   }
 
-  // Get all region content set with drupal_add_region_content().
-  foreach (array_keys($regions) as $region) {
-    // Assign region to a region variable.
-    $region_content = drupal_get_region_content($region);
-    isset($variables[$region]) ? $variables[$region] .= $region_content : $variables[$region] = $region_content;
+  foreach (system_region_list($GLOBALS['theme']) as $region_key => $region_name) {
+    if (!isset($variables[$region_key])) {
+      $variables[$region_key] = array();
+    }
+    // Append region content set with drupal_add_region_content() as markup.
+    if ($region_content = drupal_get_region_content($region_key)) {
+      $variables[$region_key][]['#markup'] = $region_content;
+    }
   }
 
   // Setup layout variable.
@@ -2865,11 +2865,9 @@ function template_preprocess_maintenance_page(&$variables) {
     $variables['layout'] = ($variables['layout'] == 'first') ? 'both' : 'second';
   }
 
-  $site_config = Drupal::config('system.site');
+  // Construct the page title.
   $site_name = $site_config->get('name');
   $site_slogan = $site_config->get('slogan');
-
-   // Construct the page title.
   if (isset($variables['page']['#title'])) {
     $head_title = array(
       'title' => strip_tags($variables['page']['#title']),