The known Schroeder paradox, i.e., a difference in the degree of swelling of ion-exchange polymers at equilibrium with liquid water and its vapor, has been discussed. It has been noted that there is no paradoxicality in this phenomenon. An example of different “swelling” based on trivial physical considerations has been presented. A simple mechanism has been proposed for increased swelling of an ion-exchange polymer immersed in liquid water, this mechanism being associated with the action of the Maxwell stresses at a polymer/electrolyte interface. The predicted values of the “excess” swelling have been shown to correspond to the data of real experiments.