A retroactive device as part of a hydraulic servo-steering system that also includes a hydraulic servo-valve device, the retroactive device comprising an arrangement for hydraulically producing a restoring moment into a central position that produces the restoring moment as a function of the pressure differential between a pressure side and a low-pressure side. The system has at least one valve arrangement that, when pressure is applied in the central position of the servo-valve, is adapted to produce a pressure differential between the external and internal chambers of the valve. The valve arrangement is disposed hydraulically in series with the retroactive device.