Foam decay may arise from liquid drainage, whether gravitational, due to interbubble gas diffusion, or from rupture of the interbubble liquid lamellae. In our study of factors affecting foam stability, we focus on interbubble gas diffusion, which works against stability even given a stable lamella. We show that liquid drainage from the foam due to such diffusion (as distinct from that due to gravitation) can often be greatly reduced by adding a water-insoluble vapor to the foam-generating gas : the presence of such a vapor counterbalances the Ostwald ripening, thus stabilizing the system.