A hydraulic arrangement for braking a trailer comprises a brake line connected between a brake system of a trailer and a trailer brake valve. The trailer brake valve is activated via a first control-pressure line which extends between the brake line and the trailer brake valve and via a second control-pressure line which extends between the trailer brake valve and a control-pressure source and acts in opposition to the pressure imposed on the trailer brake valve by the first control-pressure line. An adjustable pressure-reducing means for controlling the control pressure in the second control-pressure line is arranged in the second control-pressure line. It is proposed to design the control-pressure source as part of a hydraulic control of a brake system of a traction vehicle drawing the trailer and to force the pressure-reducing means mechanically into an open basic position by means of an adjustable prestressing force.