diff --git a/packages/validator/src/Validator/MessageTranslator.php b/packages/validator/src/Validator/MessageTranslator.php
index c9e3955b..4df81faa 100644
--- a/packages/validator/src/Validator/MessageTranslator.php
+++ b/packages/validator/src/Validator/MessageTranslator.php
@@ -59,7 +59,7 @@ public function addResource(array $items)
      *
      * @throws \InvalidArgumentException If the locale contains invalid characters
      */
-    public function trans(string $id, array $parameters = [], string $domain = null, string $locale = null)
+    public function trans(string $id, array $parameters = [], string $domain = null, string $locale = null): string
     {
         return $this->getValue($id);
     }