This is getting very annoying: I make a call, I put the phone to my head, and the screen goes black. Good. This is to stop my face from pressing the buttons on the screen. However, on my Nexus 5, the blackscreen does not prevent any interactions with the face buttons. During a call, I can hear the key tones being pressed, and on two occasions, I have disconnected from the call because my face is hitting the disconnect button. This is unacceptable. How can I fix this?