diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index a24330d..6ab892a 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -689,7 +689,7 @@ public function prepareForm($form_id, &$form, FormStateInterface &$form_state) {
     }
 
     $form += $this->elementInfo->getInfo('form');
-    $form += array('#tree' => FALSE, '#parents' => array());
+    $form += array('#tree' => TRUE, '#parents' => array());
     $form['#validate'][] = '::validateForm';
     $form['#submit'][] = '::submitForm';