OnGUI not showing in VR

I have included the following line to show a simple timer in the top left corner of a scene, which works of course, but when I tick the Virtual Reality Supported check-box and put on an Oculus Rift, it disappears.

void OnGUI()
    GUI.Label( new Rect(10, 10, 100, 20), Time.time.ToString() );

What am I missing? What should I do additionally to resolve this?

OnGUI does not work in VR-mode, you need to render your GUI to a 3D object.