Screen.lockCursor on OSX brings up Apple menu

I'm trying to hide the mouse cursor, for which I use Screen.lockCursor. The problem is that on Mac OSX when I'm using the standalone player in full screen mode (mode "FullscreenWindow") if I left click then it brings down the Apple menu on the top left of the screen.

I'm sure I'm just missing something simple as I haven't been able to find this question anywhere with Google or on here.