The invention relates to closure, in particular for a nutrient medium container, wherein a lower part can be covered by an upper part, wherein the lower part and the upper part can be locked against each other by means of at least one locking receptacle and at least one locking part by rotating the lower part and the upper part about a longitudinal axis, and wherein the locking receptacle has a receptacle groove that is covered by a shoulder and that extends perpendicularly to the longitudinal axis, in which receptacle groove the locking part engages, wherein the shoulder has at least one ramp surface extending at an angle from the longitudinal axis on the outer face of the shoulder facing away from the receptacle groove.