The valve piston (2) guided within the valve body (1) is pressed into the valve seat (3) by the force of the spring (4). The control chamber (5) is connected to the B-channel via the control channels (6) within the valve piston (2). The hydraulic pressure supplied at the B-channel with the valve closed is thus also acting on the control surface (A2). This pressure keeps the valve closed and shuts off the direction of flow from the B- to the A-channel. Conversely, the non-return valve opens when the hydraulic pressure at the A-channel exceeds the hydraulic pressure at the B-channel and the spring force (4). In order to reach the initial opening of the closed valve, the hydraulic pressure within the A-channel must be greater by the factor of the control ratio A2/A1. The response behaviour of the valve is dampened by the throttling pin.