diff --git a/cookbook/validation/custom_constraint.rst b/cookbook/validation/custom_constraint.rst
index 5b88a65409c..9209d5ed532 100644
--- a/cookbook/validation/custom_constraint.rst
+++ b/cookbook/validation/custom_constraint.rst
@@ -238,7 +238,7 @@ not to the property:
         # src/Acme/BlogBundle/Resources/config/validation.yml
         Acme\DemoBundle\Entity\AcmeEntity:
             constraints:
-                Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric: ~
+                - Acme\DemoBundle\Validator\Constraints\ContainsAlphanumeric: ~
 
     .. code-block:: php-annotations