redis-py: Race condition in connection disconnect

It seems like there is a race condition in the code for Connection.disconnect(). I run redis as a celery broker, so I seem to be running into a situation where I get a TypeError: NoneType has no attribute _close(). It would appear that in one process disconnect() is being called and setting the self._sock to None while another process has already executed the if statement that checks if self._sock is None.

    def disconnect(self):
        "Disconnects from the Redis server"
        self._parser.on_disconnect()
        if self._sock is None:
            return
        try:
            self._sock.shutdown(socket.SHUT_RDWR)
            self._sock.close()
        except socket.error:
            pass
        self._sock = None