diff --git a/app/Nova/User.php b/app/Nova/User.php
index 5a35d00..9b6b2b6 100644
--- a/app/Nova/User.php
+++ b/app/Nova/User.php
@@ -81,7 +81,7 @@ class User extends Resource
 
             Text::make(__('Username'), 'username')
                 ->sortable()
-                ->rules('required', 'string', new OnlyLetters(), 'max:250')
+                ->rules('required', 'string', 'alpha_dash:ascii', 'max:250')
                 ->creationRules('unique:users,username')
                 ->updateRules('unique:users,username,{{resourceId}}'),