XF 1.4 Private Forum

I have set one category on our Xenforo Board as a private area, not viewable by normal registered users. I set it up so that they can view the Category and the Forums, but not the threads inside.
When they click on the forums, it lets them go in, and the forums just appear empty.
Is it possible to change something so that they get an error message or something when they try to click in, rather then it just appearing that there is no content??