JS script can't recognize C# script after Unity upgrade

I upgraded to Unity 4.3.4 yesterday and now one of my scripts can't seem to recognize the 'type' of a C# script anymore. The specific script is AIFollow.cs from the AstarPathfinding project. I was using this line:

var followAI : AIFollow;

But now that results in an error:

BCE0018: The name 'AIFollow' does not denote a valid type ('not found').

The mono behavior AIFollow is still there in the AIFollow.cs script however. What's gone wrong?