  Vector-like quarks, usually dubbed top partners, are a common presence in
composite Higgs models. Being composite objects, their mass is expected to be
of the order of their inverse size, that is the condensation scale of the new
strong interactions. Light top partners, while not being a generic prediction,
are however often considered in phenomenological models. We suggest that their
lightness may be due to the matching of global 't Hooft anomalies of the
underlying theory. We check this mechanism in explicit models showing that, in
one case, composite fermions with the quantum numbers of the top quark obtain a
mass which is controlled by a soft breaking term and can be made parametrically
small.
