An elementary discussion is given of the basic equations for slowing of a proton in an electron gas with magnetic field. For large impact parameter the result is sensitive to the way in which the divergent integral is cut off at the lower limit. The most straightforward procedure gives the same force along the direction of the proton velocity, but only one half of that at right angles to it, as compared with previous results. However, a compensating modification of the small impact parameter contribution is found. The combined result is as before.