Empirical force fields' predictive power can be limited by the quality of their parameters. Parameters are not always available for all relevant chemistry, or may not be of equal quality for all chemistry of interest. For example, experiments for all components of the SAMPL7 host-guest challenge were done in sodium phosphate buffer (of varying concentration and pH). However, because of concerns about the quality of phosphate force field parameters, we conducted our reference calculations in sodium chloride (of the same ionic strength) instead. While this choice seems reasonable and is not uncommon in molecular modeling, it might affect computed free energies.