protected function _validateNumber($value, $column) {
        // Not much to check, since 0 is falsy but also a valid integer value.
        if (is_null($value)) {
            throw new Garp_Model_Validator_Exception(
                sprintf(__('%s is a required field'), __(Garp_Util_String::underscoredToReadable($column)))
            );
        }
    }