A closed quantum system thermalizes in the sense of typicality, if any initial state will reach a suitable equilibrium subspace and stay there most of the time. For non-degenerate Hamiltonians, a sufficient condition for thermalization is the eigenstate thermalization hypothesis (ETH). Shiraishi and Tasaki recently proved the ETH for a perturbation of the Hamiltonian of free fermions on a one-dimensional lattice. The perturbation is needed to remove the high degeneracies of the Hamiltonian. We point out that also for degenerate Hamiltonians ETH implies thermalization. Additionally, we develop another strategy for proving thermalization by adding small generic perturbations. This is joint work with Stefan Teufel, Roderich Tumulka, and Cornelia Vogel.