Melt segregation can be driven by suction applied to the free surface of a partially molten region (dynamic forcing). Dynamic forcing may play a role in drawing melt towards eruptin centers or in maintaining melt channels within the mantle. I examine the importance of dynamic forcing by means of a model in which is extracted by suction from a deformable porous medium with initially uniform porosity. The suction rapidly reduces the porosity near the free surface, and the melt extraction rate drops to zero after about 103 yr. The total volume of melt extracted during this time is only about 0.05 km3 per km2 of free surface area. These results suggest that the dynamic forcing probability plays a negligible role in melt segregation, and that melt channels are unlikely to exist in the mantle.