diff --git a/core/core.api.php b/core/core.api.php
index 20c324e901392535c80c18b53894486cedd19130..1d4c26319cf79802cc285898d78a2486a68a05cc 100644
--- a/core/core.api.php
+++ b/core/core.api.php
@@ -2275,7 +2275,7 @@ function hook_config_schema_info_alter(&$definitions) {
  * @see \Drupal\Core\Validation\Annotation\Constraint
  */
 function hook_validation_constraint_alter(array &$definitions) {
-  $definitions['Null']['class'] = '\Drupal\mymodule\Validator\Constraints\MyClass';
+  $definitions['Null']['class'] = '\Drupal\mymodule\Plugin\Validation\Constraints\MyClass';
 }
 
 /**