我得到致命的错误，当我去航运页面在Magento (ver 1.9)。它说：
致命错误：在/home/www/www.example.com的第439行未找到类"Zend_Measure_Weight"mysite.com/www/newsite/app/code/core/Mage/Usa/Model/Shipping/Carrier/Dhl/International.php on line 439
我在第439行有这样的代码：

'dimensions_variables'  => array(
                'L'         => Zend_Measure_Weight::POUND,
                'LB'        => Zend_Measure_Weight::POUND,
                'POUND'     => Zend_Measure_Weight::POUND,
                'K'         => Zend_Measure_Weight::KILOGRAM,
                'KG'        => Zend_Measure_Weight::KILOGRAM,
                'KILOGRAM'  => Zend_Measure_Weight::KILOGRAM,
                'I'         => Zend_Measure_Length::INCH,
                'IN'        => Zend_Measure_Length::INCH,
                'INCH'      => Zend_Measure_Length::INCH,
                'C'         => Zend_Measure_Length::CENTIMETER,
                'CM'        => Zend_Measure_Length::CENTIMETER,
                'CENTIMETER'=> Zend_Measure_Length::CENTIMETER,

            )

我该怎么修呢？