How to make two objects connected by a joint collide?

I have a spaceship, controlled by physics, and a cube as “cargo”. I want to use a spring joint as a tractor beam. It works pretty well, but I noticed that the two objects do not collide.

How do I make them collide?

So I continued to play around and I found a solution.

I made a third (empty) object to act as a middleman between the space ship and the cargo. I connected the ship to the middleman with a spring then the middleman to the cargo with a fixed joint.