Abstract: Brake lock in a fluid operated braking system is automatically suppressed by a brake diminishing cylinder and piston unit between the master cylinder and at least one wheel brake cylinder. Spring pressure upon the brake diminishing piston is normally over-balanced by a backstop pressure which is monitored by a wheel sensor. When a brake lock is imminent the backstop pressure drops and causes shifting of the brake diminishing piston from a first position in which it connects the main cylinder with the wheel cylinder into a second position in which it disconnects the main cylinder from the wheel cylinder and lowers the fluid pressure in the latter. Timely restoration of the backstop fluid pressure is insured by electrical contact elements disposed on the brake diminishing piston and engageable with complementary electrical contacts on the brake diminishing cylinder and functional to cause increased backstop pressure to be applied.