A transport lock for a clutch release system, in particular for a slave cylinder of a motor vehicle, is provided having an axially movable piston and a clutch release bearing that is connected to the piston being arranged concentrically on a housing. In order to lock the piston or the clutch release bearing during transport, a retaining ring which has a collar that extends outwards in a radial direction and which is secured on the housing in an inner cavity of the clutch release bearing is provided. A contact surface of the piston lies against the collar of the retaining ring in such a way that the retaining ring restricts the axial movement of the piston.