A hydraulic system for an aircraft includes a master cylinder, a wheel brake, a pressure supply, a reservoir, and a shut-off valve in communication with the master cylinder, the wheel brake, the pressure supply and the reservoir. The shut-off valve can include a seal that is configured to preclude fluid flow between the pressure supply and the reservoir through the valve. The shut-off valve can be operable in a first position which blocks fluid flow between the pressure supply and the wheel brake through the valve and a second position which allows fluid flow between the pressure supply and the wheel brake through the valve. Fluid pressure from the master cylinder can control operation of the valve between the first position and the second position. Failure of the seal can result in fluid flow from the brake pressure supply toward the master cylinder.