Problem using IgnoreCollision

I´m trying to use Physics.IgnoreCollision between a ship and the bullets it shots.My ship has a rigidbody and a compound collider attached.If I use:
IgnoreCollision(bullet.collider,transform.root.collider)
Unity tell me transform.root has not a collider and a script is trying to access it!
But the transform.root (the ship) has a collider (a compound collider) and I don´t understand that error warning, because it doesn’t make sense.
Thank you.

You need to call IgnoreCollision on every individual collider in the compound collider. You can do transform.root.GetComponents(Collider) to get them all.

OK, thank you Matthew.