How can I get python's Maildir to read the updated state?

I've written some code in python that opens the Maildir, updates "new" messages to be in "cur", flushes and closes the mail dir. The problem is that when I read the very same Maildir again after this using the script, it's still reading all emails as new!

(if I actually have a look in the OS directly, I can the see that the mail files have been moved from Maildir/new to Maildir/cur)

Any ideas?

mail = Maildir(self._mail_dir, factory=MaildirMessage)
mail.lock()
for i, (key, m) in enumerate(mail.iteritems()):
  if m.get_subdir() == "new":
    m.set_subdir("cur")
    m.add_flag("S")  # Message seen
    mail[key] = m
  do_something_else(m) 
mail.flush() 
mail.close()

Thanks in advance!

Solution

Finally found the fix. Basically I only need to pass factory=None instead of factory=MaildirMessage.

Reading the documentation in the link below it seems like factory=None actually picks MaildirMessage factory but apparently it also adds extra behavior.

http://docs.python.org/2/library/mailbox.html#maildir