A check valve assembly having an inlet and an outlet for medical fluids, comprising a valve body, wherein the check valve assembly in an initial state allows a flow of a working fluid and/or a sterilization fluid through the check valve assembly in both directions of flow, that is from the inlet to the outlet and vice versa, and wherein the check valve assembly in an operating state allows only one direction of flow of the working fluid, wherein the check valve assembly comprises a pin-pin-reception connection, which is embodied so that the check valve assembly can be transferred from the initial state into the operating state by applying force on the pin-pin-reception connection and/or by an impression of path on the pin-pin-reception connection.