Testing the dependence of metallicity inference on different extinction coefficients has the following expected outcome: the higher the extinction, the higher the uncertainty. We used one set of stellar parameters and metallicity, i.e., T_eff = 5500 K, log g = 3.5 dex, and [Fe/H] = −2 dex, but various relative carbon abundances. On the top are the σ_[Fe/H] and bias in bins of extinctions, and in the bottom the results are also in bins of different [C/Fe].