A system for compressing a cryogenic gas, particularly a hydrocarbon gas, has a compressor for compressing the gas and a line arrangement, which passes the gas to the intake side of the compressor and passes the compressed gas to a subsequent device for use. The line arrangement has a bypass and the compressed gas can be passed back to the intake side of the compressor via the bypass. An expander is disposed in the bypass, for re-cooling the gas that flows through the bypass. A method regulates a system for compressing a cryogenic gas, particularly a hydrocarbon gas that occurs during storage of a cryogenic liquid.