Compound collider does not trigger the parent

Hi

I have a spaceship made of a textured cube. I attached 3 child cubes to make a realistic collision detections, placed on the back reactors and the wings, mesh renderer disabled. All the cubes have colliders and rigid bodies. The scripts say that i can trigger the OnCollisionEnter of the parent (main box), and when i touch the child, it trigger the OnCollisionEnter of the child.

Now the problem is: When i touch the child collider, the OnCollisionEnter of the parent is not called.

Can someone help me please? Thank you.