diff --git a/core/lib/Drupal/Core/Form/FormStateInterface.php b/core/lib/Drupal/Core/Form/FormStateInterface.php
index 24ceb52..612cea0 100644
--- a/core/lib/Drupal/Core/Form/FormStateInterface.php
+++ b/core/lib/Drupal/Core/Form/FormStateInterface.php
@@ -23,6 +23,7 @@
  * @see \Drupal\Core\Form\FormBuilderInterface
  * @see \Drupal\Core\Form\FormValidatorInterface
  * @see \Drupal\Core\Form\FormSubmitterInterface
+ * @ingroup form_api
  */
 interface FormStateInterface {