diff --git a/tiramisu/value.py b/tiramisu/value.py
index db3b8f8..4ebc073 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -20,7 +20,8 @@
 # the rough pypy's guys: http://codespeak.net/svn/pypy/dist/pypy/config/
 # the whole pypy projet is under MIT licence
 # ____________________________________________________________
-from tiramisu.error import NoValueReturned, MandatoryError, MultiTypeError
+from tiramisu.error import NoValueReturned, MandatoryError, MultiTypeError, \
+    ConfigError
 from tiramisu.setting import owners, multitypes
 
 class Values(object):
@@ -161,12 +162,12 @@ class Values(object):
                     # this result **shall not** be a list
                     if isinstance(result, list):
                         raise ConfigError('invalid calculated value returned '
-                            'for option {0} : shall not be a list'.format(name))
+                            'for option {0} : shall not be a list'.format(opt._name))
                     value = result
                 if value != None and not opt.validate(value,
                             self.context._cfgimpl_settings.validator):
                     raise ConfigError('invalid calculated value returned'
-                        ' for option {0}'.format(name))
+                        ' for option {0}'.format(opt._name))
         # frozen and force default
         if not opt.has_callback() and opt.is_forced_on_freeze():
             value = opt.getdefault()