granite:class and granite:data for select?

Hello,

I just finished watching this presentation: https://seminars.adobeconnect.com/p43ucnv6655/?proto=true

I am trying to add a granite:class property to my granite/ui/components/foundation/form/select widget.

I was able to add this to a textfield, but it doesn't appear to be working for the select field.

Can someone please advise on how to go about adding this property?

Thanks, Matt