OnTriggerEnter not working with CharacterController

So I have a Player with a CharacterController attached to it, and I want it to collide with a collider that has isTrigger set to true, but when the player enters that collider, it doesn't detect anything, even though the collider is touching the CharacterController. it worked when I made the isTrigger collider bigger for some reason though... (I would really like to know why) but I need to have the isTrigger collider as small as possible. (it collides fine with rigidbodies)