diff --git a/kursy/oauth_validators.py b/kursy/oauth_validators.py
index 6621e74..fae85b4 100644
--- a/kursy/oauth_validators.py
+++ b/kursy/oauth_validators.py
@@ -6,6 +6,6 @@ class CustomOAuth2Validator(OAuth2Validator):
         print("get_additional_claims", request.user)
         return {
             "name": " ".join([request.user.first_name, request.user.last_name]),
-            "preferred_username": f"studio77-{request.user.username}",
+            "preferred_username": f"studio77-{request.user.id}",
             "email": request.user.email,
         }