if statement not working

var Enemy : GameObject;

var Spawn_Enemys : GameObject;

var SpawnPosition : Transform;

var isCreated: boolean;

function Start ()

{

isCreated = false;

}

function OnTriggerEnter (Spawn_Enemys : Collider)

{

if (isCreated = false)
{

	//Spawns enemy

	Instantiate(Enemy, SpawnPosition.transform.position, SpawnPosition.transform.rotation);

	isCreated = true;
}

}

if (isCreated = false)

to

if (isCreated == false)