A hydraulic brake booster includes a housing which substantially defines a pressure chamber and the housing slidably supports a control valve for communicating pressurized fluid to the pressure chamber. A piston is movably disposed within the housing to move in response to pressurized fluid within the pressure chamber and the piston substantially defines a storage chamber located inside the piston. A charging valve communicates pressurized fluid to the storage chamber and a relief valve vents the storage chamber to the pressure chamber when the pressure stored in the storage chamber is above a predetermined value. An input member cooperates with the piston to define an actuating cavity which communicates with the relief valve so that the input member is movable relative to the piston to pressurize the actuating cavity which causes the relief valve to open communication between the storage chamber and the pressure chamber.