A closure assembly configured to be mounted on a neck of a container, which closure assembly comprises a cap with a dispensing opening, and a self-closing dispensing valve attached to the cap such that it is located adjacent the dispensing opening, and wherein the dispensing cap comprises a cylindrical shaped body section having a central axis, which cylindrical body section defines an inner space extending along said central axis, an access opening at one end of the inner space for inserting the neck of the container into the inner space, and a top wall at another end of the inner space, which top wall has an inside surface facing the inner space and an outside surface facing the opposite direction, and which top wall is provided with the dispensing opening for dispensing the contents of the container, and wherein the inside surface of the top wall defines a substantially flat and annular attachment area, which attachment area extends around the dispensing opening, and which inside surface defines an annular rib, which rib is located between the attachment area and the dispensing opening, which rib protrudes relative to the substantially flat attachment area; the dispensing valve is a disc of foil material having a central valve area in which at least one self-closing slit is located and an annular peripheral attachment area extending around the central valve area, with which attachment area the dispensing valve is attached to the attachment area of the dispensing cap, by way of heat sealing, such that its central valve area aligns with the dispensing opening of the dispensing cap to close off that dispensing opening, and wherein the annular rib offsets the central valve area of the dispensing valve relative to the substantially flat attachment area of the cap. the dispensing cap comprises a cylindrical shaped body section having a central axis, which cylindrical body section defines an inner space extending along said central axis, an access opening at one end of the inner space for inserting the neck of the container into the inner space, and a top wall at another end of the inner space, which top wall has an inside surface facing the inner space and an outside surface facing the opposite direction, and which top wall is provided with the dispensing opening for dispensing the contents of the container, and wherein the inside surface of the top wall defines a substantially flat and annular attachment area, which attachment area extends around the dispensing opening, and which inside surface defines an annular rib, which rib is located between the attachment area and the dispensing opening, which rib protrudes relative to the substantially flat attachment area; the dispensing valve is a disc of foil material having a central valve area in which at least one self-closing slit is located and an annular peripheral attachment area extending around the central valve area, with which attachment area the dispensing valve is attached to the attachment area of the dispensing cap, by way of heat sealing, such that its central valve area aligns with the dispensing opening of the dispensing cap to close off that dispensing opening, and wherein the annular rib offsets the central valve area of the dispensing valve relative to the substantially flat attachment area of the cap.