A previous calculation of the single‐mode nonlinear saturation of the bump‐on‐tail instability assumed immobile ions. Here, the ions are also allowed to respond. The usual van Kampen continuum of real eigenmodes is shown to change to a double continuum. The analog of the Case class 1cmode is now singular and has an undetermined coefficient. The corresponding charge density is however nonsingular. The nonlinear calculation carries through as before, and the result is an obvious generalization of the one‐component case. Total energy and momentum are conserved, but the partition of momentum and energy between ions and electrons is not determined by asymptotic considerations alone. The result also applies to the threshold region for the ion‐sound instability.