Parking lock for fixating a transmission, in particular a transmission of a motor vehicle, comprising: - a piston for the mechanical locking of the transmission, - an electromagnetic actuator for fixating the piston in a first position which releases the transmission, having an energizable coil arranged in a magnetic actuator housing, an anchor, which is movable when the coil is energized and having an actuator plunger, which is mounted in the actuator housing and which comprises an actuating element for actuating a locking mechanism, by means of which the first position of the piston relative to the actuator housing is fixated, - a piston housing, in which the piston is movably arranged along a longitudinal axis (X-X), having a through opening implemented coaxially to the longitudinal axis (X-X) which extends between a first side, which faces the electromagnetic actuator, and a second side, - wherein the piston encloses, together with the piston housing, a pressure chamber, - wherein the piston housing comprises at least one control opening, through which a medium can be introduced into the pressure chamber, - wherein the piston housing is closed on the side facing away from the actuator housing by means of a cover and the piston comprises a spring shoe on the side facing the cover, and - wherein a compression spring is supported in the piston house in the longitudinal axis (X-X) at one end on the spring shoe, characterized in that - the compression spring is supported in the piston house in the longitudinal axis (X-X) at the other end on the cover of the piston housing, - the piston housing is made of plastic and is connected to the actuator housing at a connection point by means of a metal-plastic connection, - the electromagnetic actuator is implemented to fixate the piston in a second position which locks the transmission, - the second position of the piston relative to the actuator housing is determined by the actuating element, - the introduction of the medium into the pressure chamber suits to push the piston against the spring force of the compression spring along the longitudinal axis (X-X) from the first position into the second position, - the piston comprises a slide block which is held guided and mounted on the actuator housing, and - the slide block is formed by a slide bush inserted in the piston. - a piston for the mechanical locking of the transmission, - an electromagnetic actuator for fixating the piston in a first position which releases the transmission, having an energizable coil arranged in a magnetic actuator housing, an anchor, which is movable when the coil is energized and having an actuator plunger, which is mounted in the actuator housing and which comprises an actuating element for actuating a locking mechanism, by means of which the first position of the piston relative to the actuator housing is fixated, - a piston housing, in which the piston is movably arranged along a longitudinal axis (X-X), having a through opening implemented coaxially to the longitudinal axis (X-X) which extends between a first side, which faces the electromagnetic actuator, and a second side, - wherein the piston encloses, together with the piston housing, a pressure chamber, - wherein the piston housing comprises at least one control opening, through which a medium can be introduced into the pressure chamber, - wherein the piston housing is closed on the side facing away from the actuator housing by means of a cover and the piston comprises a spring shoe on the side facing the cover, and - wherein a compression spring is supported in the piston house in the longitudinal axis (X-X) at one end on the spring shoe, - the compression spring is supported in the piston house in the longitudinal axis (X-X) at the other end on the cover of the piston housing, - the piston housing is made of plastic and is connected to the actuator housing at a connection point by means of a metal-plastic connection, - the electromagnetic actuator is implemented to fixate the piston in a second position which locks the transmission, - the second position of the piston relative to the actuator housing is determined by the actuating element, - the introduction of the medium into the pressure chamber suits to push the piston against the spring force of the compression spring along the longitudinal axis (X-X) from the first position into the second position, - the piston comprises a slide block which is held guided and mounted on the actuator housing, and - the slide block is formed by a slide bush inserted in the piston.