diff --git a/form/type_guesser.rst b/form/type_guesser.rst
index 3d5cdfecc25..8b1cf0f52a1 100644
--- a/form/type_guesser.rst
+++ b/form/type_guesser.rst
@@ -188,7 +188,8 @@ and tag it with ``form.type_guesser``:
         services:
             # ...
 
-            AppBundle\Form\TypeGuesser\PHPDocTypeGuesser: [form.type_guesser]
+            AppBundle\Form\TypeGuesser\PHPDocTypeGuesser:
+                tags: [form.type_guesser]
 
     .. code-block:: xml