Script error: OnTriggerEnter

I'm getting a Script error.

"Script error: OnTriggerEnter

This message parameter has to be of type: Collider"

I have no clue why it gives an error like that. Any ideas?

Here's my script!

static var addgoal = 0;

var blockblue : Texture;

var blockgreen : Texture;

function Update () {

 if(addgoal == 0)
 {
     renderer.material.SetTexture("_MainTex", blockblue);
 }
 if(addgoal == 1)
 {
     renderer.material.SetTexture("_MainTex", blockgreen);
 }

}

function OnTriggerEnter (hit : Collision) {

 if(hit.gameObject.name == "Sensor")
 {
     addgoal = 1;
 }

 

}