diff --git a/form/form_themes.rst b/form/form_themes.rst
index 1b5a3594a2d..92f08b5de4b 100644
--- a/form/form_themes.rst
+++ b/form/form_themes.rst
@@ -337,7 +337,7 @@ following complex example where a ``TaskManagerType`` has a collection of
         }
     }
 
-    class TaskType
+    class TaskType extends AbstractType
     {
         public function buildForm(FormBuilderInterface $builder, array $options = []): void
         {