Using a top level variable in a class

Hey,

I have a problem with using a variable that I declared outside the class, in a class. I already have spent hours searching for an answer on the forum, but didn't find anything. If I try this, Unity acts as if the variable doesn't exist. Here is my code (I simplified it):

 #pragma strict
 var chunkWidth=49;
 class Chunk{
     var width:short;
     var position:Vector3;
     function Chunk(pos:Vector3){
         this.width=chunkWidth; //this gives the error: Unknown identifier: 'chunkWidth'.
         this.position=pos;
     }
 }

This error also occurs when I want to use a function within the class.