diff --git a/app/auth/models.py b/app/auth/models.py
index a3a0c3e47e7f4b1dbb10ad85c286d2b3dee310a7..1fd96ff9fbd68b47f5c5b6ae25a092dece5dd165 100644
--- a/app/auth/models.py
+++ b/app/auth/models.py
@@ -416,7 +416,7 @@ class User(UserMixin, ScoDocModel):
             args, excluded={"cas_id", "user_name", "roles_string", "roles"}
         )
 
-        new_cas_id = args.get("cas_id")
+        new_cas_id = args.get("cas_id", "").strip() or None
         if ScoDocSiteConfig.cas_uid_use_scodoc():
             new_cas_id = self.user_name
         else: