© 2015 IOP Publishing Ltd. The approach to the treatment of mass in relativistic mechanics advocated in the article by Keith Atkin in the January 2015 issue of Physics Education (2015 Phys. Educ. 50 46) conflicts with the viewpoint promoted of many eminent physicists for over half a century. This comment attempts to explain some of the ideas behind the latter approach and to illustrate how it helps to simplify the teaching and learning of the topic.