Submit Files in Admin Form - Magento 1.7

Question

app/code/local/Mage/Adminhtml/Block/Permissions/User/Edit/Tab/Main.php

inside: protected function _prepareForm() I added:

$form = new Varien_Data_form(array(
                'id' => 'edit_form',
                'action' => $this->getUrl('*/*/save', array('id' => $this->getRequest()->getParam('id'))),
                'method' => 'post',
                'enctype' => 'multipart/form-data'
            )
        );

However when the form is created and I inspect element it doesn't have the property of enctype="multipart/form-data"?