GameObject variable not appearing in Inspector?

I have a couple lines of code:

 public var moveSpeed : float = 8.0;
 public var spinSpeed : float = 90.0;
 public var targetObj : GameObject = null;

moveSpeed and spinSpeed appear in the inspector for the script but targetObj does not. Any ideas? I've reset the script, attached and detached it multiple times and nothing seems to update the ui for the script to represent the GameObject.

I've also tried:

 public var moveSpeed : float = 8.0;
 public var spinSpeed : float = 90.0;
 public var targetObj : GameObject;

But that didn't work either. I'm sure I'm missing something really obvious and stupid.