Abstract: The invention relates to an annular-gap seal (20) for a valve, which is designed to block the flow of a fluid from a high-pressure side to a low-pressure side in the blocked position. The valve has a cylinder, through which the fluid flows and in which a piston can be axially displaced. In the blocked position, an annular gap between the piston and the cylinder can be sealed by the annular gap seal (20), which lies in a groove that runs around the cylinder. The aim of the invention is to increase the sealing action of the annular-gap seal (20), in particular to achieve an automatic increase of the sealing action when the pressure differential between the high-pressure side and the low-pressure side increases and to guarantee the sealing action both in the designated flow direction and against the designated flow direction. To achieve this, two sealing rings (24, 25) lie adjacent to one another mirror-symmetrically in the groove.