Galaxy S4 CM12.1 5.1.1- Screen Goes Black During Phone Calls

i just flashed cm12.1 onto my phone its running 5.1.1 and when i go to call somebody after i press call the screen instantly goes black and it wont wake back up no matter what i press until the other person hangs up. i dont have a screen protector so that cant be the problem. Anybody have any ideas?