diff --git a/trytond/protocols/dispatcher.py b/trytond/protocols/dispatcher.py
index 5197cba9eb..11c875a79a 100644
--- a/trytond/protocols/dispatcher.py
+++ b/trytond/protocols/dispatcher.py
@@ -112,7 +112,7 @@ def dispatch(host, port, protocol, database_name, user, session, object_type,
                 pool.init()
             obj = pool.get(object_name, type=object_type)
             if method not in obj._rpc:
-                raise Exception('Calling method %s on ' \
+                raise Exception('UserError', 'Calling method %s on ' \
                         '%s %s is not allowed!' % \
                         (method, object_type, object_name))