Magento

I found some problems when I develop a new modules. In the backend form, I can’t define a input element of image type to a required-entry, which is the mark of required ,I found the source in lib\Varien\Data\Form\Element\image.php line 67 is
this->setClass(’input-file’);
maybe it should be this->addClass(’input-file’); so that we can remain other classes in setting.

I found it all the same both in Magento 1.5 and 1.6 CE.
Is it a bug or not?

$fieldset->addField(’module_image’, ‘image’, array(
‘label’ => Mage::helper(’module’)->__(’image-input’),
‘class’ => ‘required-entry’,
‘required’ => true,
‘name’ => module_image’,

));