An all-wheel steering system has a servomotor (10) for the rear wheels, which comprises two fixed working pistons (25 and 25A) on a piston rod (24) and two slidable control pistons (27 and 27A) in a housing section situated between said working pistons (25 and 25A). The working pistons (25 and 25A) form with the control pistons (27 and 27A) control spaces (28 and 28A) which are permanently connected to the pump (2). A pressure chamber (33) is situated between the control pistons (27 and 27A) and includes a spring element (34) which acts on the control pistons (27 and 27A). Said pressure chamber (33) can be blocked or connected with a tank (3) by a 2/2 directional valve (37) controlled by a switch unit (17). In the operational position of the rear-wheel steering (11), the two control pistons (27 and 27A) abut against a sleeve (35) because of the pump pressure directed into the control spaces (28 and 28A). The piston rod (24) can thus move freely in both steering directions. If the pressure in the control spaces (28 and 28A) drops because of a fault in the hydraulic circuit, the 2/2 directional valve is reversed and the control pistons (27 and 27A) move against shoulders (36 and 36A) through the force of the spring element (34). In order to delay the return movement, the control pistons (27 and 27A) force the oil from the control spaces (28 and 28A) into the tank (3) over a nozzle. The rear-wheel steering (11) is thus stopped in the straight-ahead driving position.