diff --git a/validation/custom_constraint.rst b/validation/custom_constraint.rst
index e456a6b7c5a..3ae4d1f855a 100644
--- a/validation/custom_constraint.rst
+++ b/validation/custom_constraint.rst
@@ -45,7 +45,7 @@ includes some simple default logic::
     // in the base Symfony\Component\Validator\Constraint class
     public function validatedBy()
     {
-        return get_class($this).'Validator';
+        return \get_class($this).'Validator';
     }
 
 In other words, if you create a custom ``Constraint`` (e.g. ``MyConstraint``),