Checker error when Service is down

I sometimes get this error from Checker in the logs. I think it happens when the Service is momentarily down.

2013/07/21 20:01:12 - ERROR    [Checker,0] Error in the call without callback `__repr__': KeyError: u'Service has no method __repr__'
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cms-1.1.0pre-py2.7.egg/cms/io/GeventLibrary.py", line 570, in process_data
    method_response = self.service.handle_message(message)
  File "/usr/lib/python2.7/site-packages/cms-1.1.0pre-py2.7.egg/cms/io/GeventLibrary.py", line 426, in handle_message
    raise KeyError("Service has no method " + method_name)
KeyError: u'Service has no method __repr__'
.