A new stellarator ripple-transport mechanism is predicted at the low collision frequencies characteristic of ions in a reactor plasma. A heuristic argument is used to derive an approximate diffusion coefficient whose magnitude, scaling and range of applicability agree well with the results of Monte Carlo calculations. The proposed diffusion coefficient is independent of collision frequency within its range of validity, which encompasses the parameters of most ions in a reactor. Its magnitude is smaller than previous estimates for the diffusion coefficient in this range, but larger than the diffusion coefficients in all other low-collision-frequency regimes. An explanation of the form of the diffusion coefficient is given in terms of analytic theory of ripple transport.