I have a post that should show both the toplevel category and the sublevel category both in url and on the post itself.

Choosing this in the permalink structure: /%category%/%postname%/ the url works fine, if I just select the subcateory. But then only the subcategory is displayed on the post.

And if I select both the toplevel category and the subcategory, the subcategory is removed from the URL.

I want both the toplevel and subcategory to be in the URL and have the post categorized by them both. How to do that?