[Plugin: WordPress eCommerce – MarketPress] Shortcode category in product list not working

I’m trying out Marketpress and It seems healthier than WP e-commerce. But the instructions for using product lists by short code is not working:

[mp_list_products category=”sale”] should only display sale category items on the page, but it is displaying the entire store inventory. How do I fix this issue?

http://wordpress.org/extend/plugins/wordpress-ecommerce/