diff --git a/core/lib/Drupal/Core/Render/Renderer.php b/core/lib/Drupal/Core/Render/Renderer.php
index 2746041..8a2f8dc 100644
--- a/core/lib/Drupal/Core/Render/Renderer.php
+++ b/core/lib/Drupal/Core/Render/Renderer.php
@@ -302,10 +302,14 @@ protected function doRender(&$elements, $is_root_call = FALSE) {
     // with how render cached output gets stored. This ensures that
     // #post_render_cache callbacks get the same data to work with, no matter if
     // #cache is disabled, #cache is enabled, there is a cache hit or miss.
-    $prefix = isset($elements['#prefix']) ? SafeMarkup::checkAdminXss($elements['#prefix']) : '';
-    $suffix = isset($elements['#suffix']) ? SafeMarkup::checkAdminXss($elements['#suffix']) : '';
-
-    $elements['#markup'] = $prefix . $elements['#children'] . $suffix;
+    if (isset($elements['#render_children'])) {
+      $elements['#markup'] = $elements['#children'];
+    }
+    else {
+      $prefix = isset($elements['#prefix']) ? SafeMarkup::checkAdminXss($elements['#prefix']) : '';
+      $suffix = isset($elements['#suffix']) ? SafeMarkup::checkAdminXss($elements['#suffix']) : '';
+      $elements['#markup'] = $prefix . $elements['#children'] . $suffix;
+    }
 
     // We've rendered this element (and its subtree!), now update the stack.
     $this->updateStack($elements);