Directory Categories

The Directory plugin uses it's own categories, which is separate from Wordpress' built-in categories.

I would like to add listings to my existing categories, instead of creating a new set of categories.

Using CustomPress, I am able to specify that the Directory listings should support regular categories. Perfect!

However, this does not seem to work. When I view a listing on the website, it says:
"This entry was posted in listingcategory1, listingcategory2, etc."
(It will list the Directory categories the listing is posted in. It will not list any of the Wordpress categories).

How can I add my listings to the default Wordpress categories?