diff --git a/openslides/utils/user/__init__.py b/openslides/utils/user/__init__.py
index df711f6c6..0dbc44ce4 100644
--- a/openslides/utils/user/__init__.py
+++ b/openslides/utils/user/__init__.py
@@ -145,8 +145,7 @@ class Users(object):
 
 def generate_uid(prefix, id):
     if ':' in prefix:
-        # TODO: Use the right Exception.
-        raise Exception("':' is not allowed in a the 'user_prefix'")
+        raise ValueError("':' is not allowed in a the 'user_prefix'")
     return "%s:%d" % (prefix, id)