Custom JS widget not loaded on siteadmin page

Hi,

I have created a custom multifield widget (CustomWidget.js) in my clientlibs, which is integrated into a custom tab in the page properties.

        <information

            jcr:primaryType="cq:Widget"

            fieldDescription="Press + to add more information"

            fieldLabel="Information"

            name="./information"

            xtype="multifield">

            <fieldConfig

                jcr:primaryType="cq:Widget"

                xtype="customWidget"/>

This works fine when I am on the page and open the page properties from the sidekick.

But when I am on the siteadmin page with the content tree and rigth klick on a page and choose 'properties' the multifield doesn't work. Browser console says:

Uncaught cannot create Component: xtype 'customWidget' not found and no default supplied

How can I make the JS for the widget being loaded on the siteadmin page?

Cheers,

Alex