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 eruption centers or in maintaining melt channels within the mantle. I examine the importance of dynamic forcing by means of a model in which melt 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 dynamic forcing probably plays a negligible role in melt segregation, and that melt channels are unlikely to exist in the mant