v6 NameError: global name 'wizard' is not defined

hi,
when i want to upgrade a module I have this error :

Traceback (most recent call last):
  File "osv\osv.pyo", line 57, in wrapper
  File "osv\osv.pyo", line 140, in execute
  File "osv\osv.pyo", line 130, in execute_cr
  File "d:\OpenERP allinone\Server\bin\addons\base\module\wizard\base_module_upgrade.py", line 98, in upgrade_module
NameError: global name 'wizard' is not defined

I think just add in the head of python file :
import wizard

Bye