This article comments on the wake model used in moderately loaded rotor lifting line theory for the preliminary design of propellers and horizontal-axis turbines. Mathematical analysis of the classic wake model reveals an inconsistency between the induced velocities numerically computed by the model versus those theoretically predicted by the model. An improved wake model is presented, which better agrees with theory than previous models and thus improves the numerical consistency and robustness of rotor lifting line design algorithms. The present wake model analytically relates the pitch of the trailing vortices to the pitch of the total inflow computed at the lifting line control points. For conciseness, the article focuses on the propeller case, although both propeller and horizontal-axis turbine examples are presented.