A timepiece mobile for a semi-instantaneous jump mechanism, including a stop member, an elastic return device, and a drive wheel including, around an axis a hub for guiding this movable stop member with respect to the drive wheel and including a disengageable stop finger movable between a wound position where its radial extension is maximum with respect to the axis, and an unwound position where its radial extension is minimal with respect to the axis, this stop finger being moved away from the axis by the elastic return device, and the stop member including a housing the walls of which are arranged to bearingly cooperate, during the winding of the elastic return device with a contact surface that this elastic return device includes to limit the value of the winding and to limit the deformation of the elastic return means to its elastic range only.