  A simple, but general solution is proposed for the Kohn-Luttinger problem,
i.e., the nonconvergence of the finite-temperature many-body perturbation
theory with its zero-temperature counterpart as temperature is lowered to zero
under some circumstances. How this nonconvergence can be avoided by altering
the reference wave function is illustrated numerically by using up to the fifth
order of the perturbation theory.
