diff --git a/core/lib/Drupal/Core/Render/Element/Details.php b/core/lib/Drupal/Core/Render/Element/Details.php
index e6f4474..a336730 100644
--- a/core/lib/Drupal/Core/Render/Element/Details.php
+++ b/core/lib/Drupal/Core/Render/Element/Details.php
@@ -87,6 +87,7 @@ public static function preRenderDetails($element) {
     // Loop through widgets looking for errors, make sure to enable #open if any are found.
     if (!empty($element['#parents'])) {
       $parents = implode('][', $element['#parents']);
+      if (!empty($element['#groups'][$parents])) {
         $children = Element::children($element['#groups'][$parents]);
         if (!empty($children)) {
           foreach ($children as $key) {
@@ -101,6 +102,7 @@ public static function preRenderDetails($element) {
           }
         }
       }
+    }
 
     // Do not render optional details elements if there are no children.
     if (isset($element['#parents'])) {