Nexus 4: Screen goes black when making a call

So, I applied a screen protector on my Nexus 4, and I noticed my screen going black/blank while making a call.

The screen may come back intermittently when pressing the power button, or when the call gets disconnected.

Since this started happening after applying the screen protector, I figured it should be something related to it.

It turns out, there is proximity sensor on the top left corner, which blanks out the screen to save battery power when held extremely close to your body (like making a phone call)

So I cut my screen protector near the the sensor, and now its back to normal