diff --git a/tiramisu/value.py b/tiramisu/value.py
index 329b393..0f21d8c 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -181,7 +181,7 @@ class Values(object):
 
     def setowner(self, opt, owner):
         if opt not in self._values:
-            raise ConfigError(_('no value for {1} cannot change owner to {2}').format(opt))
+            raise ConfigError(_('no value for {0} cannot change owner to {1}').format(opt._name, owner))
         if not isinstance(owner, owners.Owner):
             raise TypeError(_("invalid generic owner {0}").format(str(owner)))
         self._values[opt] = (owner, self._values[opt][1])