Forced oscillations can push dissolved volatiles into bubbles by a process called rectified diffusion. In engineering applications, the pumping action of rectified diffusion makes bubbles grow. In the geosciences, rectified diffusion is a suggested mechanism to trigger volcanic eruptions with seismic waves generated by distant earthquakes. Previous geoscience studies adopted the engineering results and proposed that in a confined system like a magma chamber, rectified diffusion causes pressure increase rather than bubble growth. However, the volcanic application is fundamentally different than engineering applications in that solubility continually changes with increasing pressure in the confined system. Here we present the first self-consistent treatment of rectified diffusion in a confined system. Evolving solubility has a significant effect. The new solution demonstrates that previous work significantly overestimated the effect of rectified diffusion in magmatic systems. For reasonable seismic wave amplitudes, the pressure change is at the most 2 ¿ 10-9 of its initial value.