BDAY parsing problems

While trying to import an existing vcard with dexter 0.18, got this traceback:

[...]
dbus.exceptions.DBusException: org.freedesktop.DBus.Python.ValueError: Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/dbus/service.py", line 702, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/bin/dexter-server", line 104, in CreateContact
    phones, addresses, imnicks, notes, self.store)
  File "/usr/lib/python2.7/site-packages/dexter/backend/serverutils.py", line 73, in create_new_contact
    int(birthdaylist[2]))
ValueError: invalid literal for int() with base 10: '04T00:00:00Z'

The birthday had this format: BDAY:1973-09-04T00:00:00Z. According to RFC2426, this should be allowed.