diff --git a/src/lib/Base/Exceptions/ContentFieldValidationException.php b/src/lib/Base/Exceptions/ContentFieldValidationException.php
index e0f646df1e..0b8091dca4 100644
--- a/src/lib/Base/Exceptions/ContentFieldValidationException.php
+++ b/src/lib/Base/Exceptions/ContentFieldValidationException.php
@@ -90,7 +90,7 @@ private function generateValidationErrorsMessages(): string
         }
 
         /** @var callable(string|\Ibexa\Contracts\Core\Repository\Values\Translation): string $convertToString */
-        $convertToString = function ($error): string {
+        $convertToString = static function ($error): string {
             return (string)$error;
         };
         $validationErrors = array_map($convertToString, $validationErrors);