We consider the two-Higgs-doublet model as a framework in which to evaluate the viability of scenarios in which the sign of the Hbb coupling is opposite to that of the Standard Model (SM), while at the same time all other tree-level couplings are close to their SM values. Whereas such a scenario is consistent with current LHC observations, both future running at the LHC and the ILC could determine the sign of the Hbb coupling. Discrimination is possible due to the interference between the b-quark and t-quark loop contributions to the ggh coupling. In addition, the charged-Higgs loop contribution to the amplitude for Higgs decay to two photons is large and fairly constant up to the largest charged-Higgs mass allowed by tree-level unitarity bounds when the Hbb coupling has the opposite sign from that of the SM.