How do I switch Auto Perspective on? I recently had an issue with Blender 2.71 RC2, which I submitted as a bug. The issue was that when I hit Numpad 1,3 or 7 the viewport would not automatically change from perspective  to orthographic  mode, as it used to in Blender 2.70.

I now want it to behave like this in blender 2.71 RC2, but I can't find the Auto Perspective check box in the user preferences. 

Where is it?
It is in the Interface> View Manipulation section: