diff --git a/flaschengeist/models/user.py b/flaschengeist/models/user.py
index f69ea1f..0d9d506 100644
--- a/flaschengeist/models/user.py
+++ b/flaschengeist/models/user.py
@@ -67,7 +67,7 @@ class User(db.Model, ModelSerializeMixin):
 
     @property
     def avatar_url(self):
-        return url_for("users.get_avatar", userid=self.userid)
+        return url_for("users.get_avatar", userid=self.userid) if self.userid else None
 
     @property
     def roles(self):