Issue with feed filters + Availability

The filters are working great for everything except Availability. For our products its either “in stock” or “out of stock”. I want to exclude all out of stock items from the feed. However following your examples that I have seen here and the link ”
detailed information and filter examples” I can’t get it to work despite refreshing the feed.

Right now it has:
IF – Availability
CONDITION – is equal to
VALUE – out of stock
THEN – Exlude.

I save it, hit the manual refresh of the feed, open the xml file and the out of stock items are still there?

<g:availability>out_of_stock</g:availability>