diff --git a/src/Symfony/Bridge/Twig/Extension/FormExtension.php b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
index cece93e89a..6e6274dcc4 100644
--- a/src/Symfony/Bridge/Twig/Extension/FormExtension.php
+++ b/src/Symfony/Bridge/Twig/Extension/FormExtension.php
@@ -166,6 +166,9 @@ class FormExtension extends AbstractExtension implements InitRuntimeInterface
         unset($this->$name);
     }
 
+    /**
+     * @internal
+     */
     public function isRootForm(FormView $formView)
     {
         return null === $formView->parent;