diff --git a/src/Bundle/ChillPersonBundle/Tests/Controller/PersonIdentifierListApiControllerTest.php b/src/Bundle/ChillPersonBundle/Tests/Controller/PersonIdentifierListApiControllerTest.php
index 87604e730..be5e771ad 100644
--- a/src/Bundle/ChillPersonBundle/Tests/Controller/PersonIdentifierListApiControllerTest.php
+++ b/src/Bundle/ChillPersonBundle/Tests/Controller/PersonIdentifierListApiControllerTest.php
@@ -79,7 +79,7 @@ class PersonIdentifierListApiControllerTest extends TestCase
                 return '';
             }
 
-            public function validate(ExecutionContextInterface $context, PersonIdentifier $identifier, PersonIdentifierDefinition $definition = null): void {}
+            public function validate(ExecutionContextInterface $context, PersonIdentifier $identifier, ?PersonIdentifierDefinition $definition = null): void {}
 
             public function getDefaultValue(PersonIdentifierDefinition $definition): array
             {