diff --git a/core/lib/Drupal/Component/Diff/DiffEngine.php b/core/lib/Drupal/Component/Diff/DiffEngine.php
index f426b96..fb4d9d7 100644
--- a/core/lib/Drupal/Component/Diff/DiffEngine.php
+++ b/core/lib/Drupal/Component/Diff/DiffEngine.php
@@ -1260,7 +1260,12 @@ function render() {
               $output .= $piece;
             }
             else {
-              $output .= theme('diff_inline_chunk', array('text' => $piece, 'type' => $chunk->type));
+              $build = array(
+                '#theme' => 'diff_inline_chunk',
+                '#text' => $piece,
+                '#type' => $chunk->type,
+              );
+              $output .= drupal_render($build);
             }
           }
           break;
@@ -1271,7 +1276,12 @@ function render() {
               $output .= $piece;
             }
             else {
-              $output .= theme('diff_inline_chunk', array('text' => $piece, 'type' => $chunk->type));
+              $build = array(
+                '#theme' => 'diff_inline_chunk',
+                '#text' => $piece,
+                '#type' => $chunk->type,
+              );
+              $output .= drupal_render($build);
             }
           }
           break;
diff --git a/core/lib/Drupal/Core/Controller/AjaxController.php b/core/lib/Drupal/Core/Controller/AjaxController.php
index 55fef94..d65108f 100644
--- a/core/lib/Drupal/Core/Controller/AjaxController.php
+++ b/core/lib/Drupal/Core/Controller/AjaxController.php
@@ -64,7 +64,8 @@ public function content(Request $request, $_content) {
         // replace the element making the ajax call. The default 'replaceWith'
         // behavior can be changed with #ajax['method'].
         $response->addCommand(new InsertCommand(NULL, $html));
-        $status_messages = theme('status_messages');
+        $build = array('#theme' => 'status_messages');
+        $status_messages = drupal_render($build);
         if (!empty($status_messages)) {
           $response->addCommand(new PrependCommand(NULL, $status_messages));
         }
diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index c2003eb..e337cc9 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -255,7 +255,11 @@ public function on500Html(FlattenException $exception, Request $request) {
     drupal_set_title(t('Error'));
     // We fallback to a maintenance page at this point, because the page
     // generation itself can generate errors.
-    $output = theme('maintenance_page', array('content' => t('The website has encountered an error. Please try again later.')));
+    $build = array(
+      '#theme' => 'maintenance_page',
+      '#content' => t('The website has encountered an error. Please try again later.'),
+    );
+    $output = drupal_render($build);
 
     $response = new Response($output, 500);
     $response->setStatusCode(500, '500 Service unavailable (with message)');
diff --git a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
index 885db53..1a62df5 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
@@ -37,7 +37,13 @@ public function onKernelRequestMaintenanceModeCheck(GetResponseEvent $event) {
       // Deliver the 503 page.
       drupal_maintenance_theme();
       drupal_set_title(t('Site under maintenance'));
-      $content = theme('maintenance_page', array('content' => filter_xss_admin(t(config('system.maintenance')->get('message'), array('@site' => config('system.site')->get('name'))))));
+      $build = array(
+        '#theme' => 'maintenance_page',
+        'content' => filter_xss_admin(
+          t(config('system.maintenance')->get('message'), array('@site' => config('system.site')->get('name')))
+        ),
+      );
+      $content = drupal_render($build);
       $response = new Response('Service unavailable', 503);
       $response->setContent($content);
       $event->setResponse($response);