gsmmodem traceback

gsmmodem.modem.GsmModem - DEBUG - write: AT+CUSD=1,"*1111111#",15
gsmmodem.modem.GsmModem - DEBUG - response: ['OK']
gsmmodem.modem.GsmModem - DEBUG - notification: ['+CUSD: 4']
Exception in thread Thread-3:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/lib64/python2.7/threading.py", line 763, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 880, in __threadedHandleModemNotification
    self._handleUssd(lines)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 1125, in _handleUssd
    self._ussdResponse = self._parseCusdResponse(lines)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 1158, in _parseCusdResponse
    sessionActive = cusdMatches[0].group(1) == '1'
AttributeError: 'NoneType' object has no attribute 'group'

Exception in thread Thread-4:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "/usr/lib64/python2.7/threading.py", line 763, in run
2014-12-19 00:42:25,554 - gsmmodem.modem.GsmModem - DEBUG - notification: ['+CUSD: 4']
    self.__target(*self.__args, **self.__kwargs)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 880, in __threadedHandleModemNotification
    self._handleUssd(lines)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 1125, in _handleUssd
    self._ussdResponse = self._parseCusdResponse(lines)
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 1158, in _parseCusdResponse
    sessionActive = cusdMatches[0].group(1) == '1'
AttributeError: 'NoneType' object has no attribute 'group'

Traceback (most recent call last):
  File "/home/jthurner/compile/python-gsmmodem/examples/ussd_demo.py", line 41, in <module>
    main()
  File "/home/jthurner/compile/python-gsmmodem/examples/ussd_demo.py", line 30, in main
    response = modem.sendUssd(USSD_STRING) # response type: gsmmodem.modem.Ussd
  File "/home/jthurner/compile/python-gsmmodem/gsmmodem/modem.py", line 706, in sendUssd
    raise TimeoutException()
gsmmodem.exceptions.TimeoutException: None

Process finished with exit code 1