Discuz with UserPro plugin: login URL problem

Hello,

I integrated Discuz and UserPro plugin as it described in Discuz plugin’s relevant admin area and that part works properly.
What doesn’t, is that if I click in a specific post’s comment area on the link: “You must be logged in to post a comment.”, it links to WP standard backend login URL like:
http://mydomain.com/wp-login.php
instead of the UserPro login popup what is enabled in UserPro and shown on frontend!
(So using this UserPro feature commenters (WP Subscribers) can register / login for commenting on frontend, not even knowing admin URL…)

What is strange, that another comment plugin without any UserPro integration handles the case correctly and links to the correct popup URL after activating and setting up UserPro.

Thanks,
best,
V.