oFGetScreenMode() not working

I’m trying to determine whether OF_FULLSCREEN is being used or OF_WINDOW in my program. The function oFGetScreenMode() should return a 0 when OF_WINDOW is being used and it should return a 1 when OF_FULLSCREEN is being used. For some reason it always returns a 0 in my program (meaning the program thinks I’m always using OF_WINDOW) even when I am in fullscreen mode. Any suggestions?