[Zope] None Object and None String

I have a Zope session variable that is set to None. When I update my MySQL database and set the value of one of my fields to the value of this session variable, the value is set to the string 'None'. Anyone encountered a similar problem? I would think that the None object would translate to the NULL database constant and not the string with value 'None'. Any help would be appreciated. Thanks. - Asad