Disable proximity sensor on Nexus 5

My Nexus 5's proximity sensor is broken and I verified the same using the Proximity Sensor Test . As usual, the screen goes black during the calls and I use the power button to end the call. But the problem is during whatsapp or skype call, power button doesn't help and I need to search for a Bluetooth or ear phones to dial or receive a call. Kindly help me to disable proximity sensor or any other work arounds Edit: Unfortunately I am not interested in rooting. So I am looking for some kind of app.