Constraints are convenient in the calculation of free energy profiles via molecular dynamics simulations, but they subtly alter the phase space distribution. In a recent letter of a related title in this journal, Wong and York [J. Chem. Theory Comput. 2012, 8, 3998–4003] suggest replacing Fixman’s mass-metric correction with its inverse and adding a Jacobian contribution to the potential of mean constraint force. This letter refutes both suggestions, discusses the underlying interpretation problems, and provides supporting numerical simulations.