We introduce a binding unanimous voting rule to a public goods game with an uncertain threshold for the total group contribution. In a laboratory experiment we find that voting generates significantly higher total contributions than making individual voluntary contributions to the public good. Heterogeneity with regard to marginal costs of contribution makes coordination on the threshold value somewhat more dificult when voting, but apparently facilitates coordination when not voting. Homogeneous non-voting groups instead exhibit a breakdown of contributions commonly observed in linear public goods games, but unusual for a threshold setting. We also notice a preference for payoff symmetry over maximization of expected welfare in heterogeneous voting groups, which to a lesser extent also appears in nonvoting groups. Using a top-down rule, i.e., splitting the voting process into two separate votes on 1) total contribution and 2) individual contributions does not affect these results.