On the full dataset of 40 cysteines and 22 histidines, we found the strongest performing force field, CHARMM36m-ECC, to exhibit an AUE of 1.61 ± 0.21 pK for cysteine; this accuracy exceeds conventional predictors and a null model. While increasing the vdW of sulfur and charge-scaling both improved the performance of Amber14SB in predicting cysteine pK a values, the final accuracy of 2.36 ± 0.29 pK remains lower than that of Charmm36m, suggesting further reparameterization of the residue would be required.