protected function validateUnitProduct()
    {
        $allowed = array(
            'size_unit' => $this->convertor->getUnitNames('size'),
            'weight_unit' => $this->convertor->getUnitNames('weight')
        );

        $fields = array(
            'size_unit' => $this->translation->text('Size unit'),
            'weight_unit' => $this->translation->text('Weight unit')
        );

        $errors = 0;

        foreach ($fields as $field => $label) {

            $value = $this->getSubmitted($field);

            if (isset($value) && !isset($allowed[$field][$value])) {
                $errors++;
                $this->setErrorUnavailable($field, $label);
            }
        }

        return empty($errors);
    }