Can't Combine in Large Sewing Kit

[loramin]

When I try to combine anything (eg. two spiderling silks) in my Large Sewing Kit I get a message "You may not have any stacks of items in the container when combining." This also happens if I just hit combine with an empty sewing kit.

I tried doing a brewing combine in the brewing barrel and it worked fine, so this seems to be exclusively a tailoring kit problem.