diff --git a/Util/FormBuilderIterator.php b/Util/FormBuilderIterator.php
index c67d68aed3d..2742afde642 100644
--- a/Util/FormBuilderIterator.php
+++ b/Util/FormBuilderIterator.php
@@ -65,12 +65,7 @@ public function __construct(FormBuilderInterface $formBuilder, $prefix = false)
      */
     private static function getKeys(FormBuilderInterface $formBuilder)
     {
-        if (!self::$reflection) {
-            self::$reflection = new \ReflectionProperty(get_class($formBuilder), 'children');
-            self::$reflection->setAccessible(true);
-        }
-
-        return array_keys(self::$reflection->getValue($formBuilder));
+        return array_keys($formBuilder->all());
     }
 
     /**