How can a composite system be a boson if it is constituted of fermions?

For example, the He-4 nucleus is considered a boson (https://en.wikipedia.org/wiki/Helium-4). But in what way is it a boson? I doesn't seem possible for a bunch of He-4 nuclei to pile up on each other in the same quantum state because protons and neutrons are fermions (made up of quarks which are also fermions).