A closure assembly for a beverage container suitable for accommodating a carbonated beverage, the beverage container having a cylindrical neck part defining a circumferential rim defining an opening and an outwardly oriented surface having an outwardly oriented circumferential flange, the closure assembly comprising a closure comprising a closure plate and a cylindrical part, said closure plate configured for covering said beverage container opening at said rim and said cylindrical part configured for covering said neck part between said rim and said circumferential flange, said cylindrical part comprising a locking part configured for arresting said outwardly oriented circumferential flange of said neck part, the closure defining an interior surface configured for facing an interior of the beverage container, and a flexible sealing ring configured to move between a first position in which said sealing ring is accommodated in a compressed state entirely within a circumferential cavity defined between said cylindrical part of said closure and said outwardly oriented surface of said neck part at a location between said rim and said circumferential flange when a pressure on the interior surface of the closure is lower than or equal to a temperature dependent internal carbonization pressure at room temperature, which is between 0°C and 60°C, and, a second position in which a larger part of said sealing ring is accommodated in a compressed state within said circumferential cavity defined between said cylindrical part of said closure and said outwardly oriented surface of said neck at a location between said rim and said circumferential flange, and a smaller part of said sealing ring is located in an uncompressed state within a groove in said cylindrical part and located adjacent said circumferential cavity for allowing fluid communication between said gas filled head space and the exterior of said beverage container when said pressure on the interior surface of the closure is higher than said temperature dependent internal carbonization pressure at room temperature. a closure comprising a closure plate and a cylindrical part, said closure plate configured for covering said beverage container opening at said rim and said cylindrical part configured for covering said neck part between said rim and said circumferential flange, said cylindrical part comprising a locking part configured for arresting said outwardly oriented circumferential flange of said neck part, the closure defining an interior surface configured for facing an interior of the beverage container, and a flexible sealing ring configured to move between a first position in which said sealing ring is accommodated in a compressed state entirely within a circumferential cavity defined between said cylindrical part of said closure and said outwardly oriented surface of said neck part at a location between said rim and said circumferential flange when a pressure on the interior surface of the closure is lower than or equal to a temperature dependent internal carbonization pressure at room temperature, which is between 0°C and 60°C, and, a second position in which a larger part of said sealing ring is accommodated in a compressed state within said circumferential cavity defined between said cylindrical part of said closure and said outwardly oriented surface of said neck at a location between said rim and said circumferential flange, and a smaller part of said sealing ring is located in an uncompressed state within a groove in said cylindrical part and located adjacent said circumferential cavity for allowing fluid communication between said gas filled head space and the exterior of said beverage container when said pressure on the interior surface of the closure is higher than said temperature dependent internal carbonization pressure at room temperature.