*_charset in Charset become unicode instance in email-4.0a. message.py should add this for type test. --- email-4.0a2/email/message.py Mon Mar 6 04:58:33 2006 +++ email/message.py Mon Mar 6 14:59:04 2006 @@ -238,7 +238,7 @@ self.del_param('charset') self._charset = None return - if isinstance(charset, str): + if isinstance(charset, str) or isinstance(charset, unicode): charset = email.charset.Charset(charset) if not isinstance(charset, email.charset.Charset): raise TypeError(charset)