A pressure medium container for hydraulic motor vehicle braking systems, with at least one chamber which can be filled with a liquid medium via a filler neck, and with a cover which can be fastened to the filler neck and has means for equalizing the pressure between the chamber and the atmosphere, wherein a sealing element is provided to prevent the liquid medium from emerging from the chamber. The sealing element has a space exposed to the atmosphere and has one or more openings facing the chamber, the space being configured such that liquid medium penetrating the space undergoes an increase in surface area, while its volume remains constant, when displaced by means of a further gaseous medium, and, when a threshold surface tension is reached, the liquid medium is forced back into the chamber such that the gaseous medium can flow into the atmosphere via the sealing element.