It is shown that second‐order (&rgr;/L) corrections in the expression for the equilibrium distribution function are required to obtain a self‐adjoint system of equations for ion cyclotron range of frequencies (ICRF) wave propagation in a nonuniform plasma (&rgr; denotes the ion‐Larmor radius andLthe gradient scale length). Self‐adjointness results in energy conservation in the absence of absorption mechanisms, as expected. A Lagrangian density is obtained, which yields both the wave operator and its adjoint, and directly results in the conservation law of the truncated system.