Ultimate Facebook - how to redirect to the page they were on

For my site I have a pop up that encourages users to login with Facebook - using the Ultimate Facebook plugin.

Once someone clicks the button and logs in, I want to redirect them to the page they were just on. (They are currently being redirected to the home page when they login, which will frustrate users, as they will have to dig around to find the article they were just reading).

In Ultimate Facebook there is a setting "Redirect on login". There is an option called "Site URL", but is it possible to tell it to redirect to whichever URL they were just on when they clicked "Login"?

Thanks!
Josh