  C. M. Will in a recent Letter [arXiv:1802.05304] predicts a new Mercury's
precession rate which is $100$ times larger than the second-post-Newtonian
contribution, our calculation is about $30$ times larger. Thus the new
Mercury's precession rate is about $6.4\ast 10^{-8}$, instead of $6.2\ast
10^{-8}$, degrees per century.
