OnTriggerExit() help

Im having trouble with OnTriggerEnter and OnTriggerExit

I have it set so that my player becomes a child of a platform when the player enters the trigger (which is an empty game object above the platform). Once this happens though I am unable to exit the trigger and remains parented to the platform. The point of the code is for the player to be parented to a platform so he/she does not fall off the platform while it moves and to become un-parented from it when they leave the trigger object. The following is my code:

 var player : GameObject;
 var platform : GameObject;
 function OnTriggerEnter(trigger : Collider)
     {
         print("enter");
         player.transform.parent = platform.transform;
 
     }
     
     
 function OnTriggerExit(trigger : Collider)
     {
         print("exit");
         player.transform.parent = null;
     }