diff --git a/framework/core/src/Core/Validator/UserValidator.php b/framework/core/src/Core/Validator/UserValidator.php
index e37f78b87..3f4fad35f 100644
--- a/framework/core/src/Core/Validator/UserValidator.php
+++ b/framework/core/src/Core/Validator/UserValidator.php
@@ -45,7 +45,7 @@ class UserValidator extends AbstractValidator
         return [
             'username' => [
                 'required',
-                'alpha_dash',
+                'regex:/^[a-z0-9_-]+$/i',
                 'unique:users,username'.$idSuffix,
                 'min:3',
                 'max:30'