def unpack(self, value):
        """Unpack the parameter using its kattype.

        Parameters
        ----------
        packed_value : str
            The unescaped KATCP string to unpack.

        Returns
        -------
        value : object
            The unpacked value.

        """
        # Wrap errors in FailReplies with information identifying the parameter
        try:
            return self._kattype.unpack(value, self.major)
        except ValueError, message:
            raise FailReply("Error in parameter %s (%s): %s" %
                            (self.position, self.name, message))