  We consider a simple, yet generic scenario in which a new heavy $Z'$ gauge
boson couples both to SM fermions and to dark matter. In this framework we
confront the best LHC limits on an extra gauge boson $Z'$ to the constraints on
couplings to dark matter from direct detection experiments. In particular we
show that the LHC searches for resonant production of dileptons and the recent
exclusion limits obtained by the LUX collaboration give complementary
constraints. Together, they impose strong bounds on the invisible branching
ratio and exclude a large part of the parameter space for generic $Z'$ models.
Our study encompasses many possible $Z'$ models, including SSM, $E_6$-inspired
or B-L scenario.
