Black Borders in VR - FOV reduction

I’m getting black rounded borders around the edges of my oculus screen that creates a reduced field of view. Here’s a video showing the difference between the ue4 aplication (with black borders) and the Oculus home menu (no borders). Dropbox - Black - Simplify your life

I’ve seen this in some other UE4 games. Any clues on which parameter is causing this?