diff --git a/src/Controller/UserController.php b/src/Controller/UserController.php
index 1f0d5cf..4b825d0 100644
--- a/src/Controller/UserController.php
+++ b/src/Controller/UserController.php
@@ -167,8 +167,8 @@ class UserController implements IAuthenticationRequired
 
         $newUsername = \Container::$request->post('username');
         if (strlen($newUsername) > 0 && $newUsername !== $user->getUsername()) {
-            if (filter_var($newUsername, FILTER_VALIDATE_EMAIL)) {
-                return new JsonContent(['error' => ['errorText' => 'Please select a username that is not a valid email address.']]);
+            if (preg_match('/^[a-zA-Z0-9_\-\.]+$/', $newUsername) !== 1) {
+                return new JsonContent(['error' => ['errorText' => 'Username can contain only english letters, digits, - (hyphen), . (dot), _ (underscore).']]);
             }
 
             if ($this->userRepository->getByUsername($newUsername) !== null) {