diff --git a/src/Core/Validator/UserValidator.php b/src/Core/Validator/UserValidator.php
index 60b63452b5..4cb9439b5e 100644
--- a/src/Core/Validator/UserValidator.php
+++ b/src/Core/Validator/UserValidator.php
@@ -46,7 +46,7 @@ protected function getRules()
         return [
             'username' => [
                 'required',
-                'regex:/^[\x{4e00}-\x{9fa5}a-z0-9_-]+$/i',
+                'regex:/^[\x{4e00}-\x{9fa5}a-z0-9_-]+$/ui',
                 'unique:users,username'.$idSuffix,
                 'min:1',
                 'max:20'