Invention relates to a fuel system (10) for feeding gas fuel to an internal combustion piston engine the system comprising one or more fuel injectors configured to inject liquid gas fuel into the engine, a fuel inlet line (26) extending from a fuel tank (18) via a high pressure pump (28) to the one or more injectors (20), and a fuel return line (30) for handling a so called return fuel from the one or more injectors, characterized in that the fuel return line (30) comprises - a separation unit configured to separate gaseous and liquid portions of the return fuel, - a first return line section (30.1) configured to return liquid portion of the return fuel from the separation unit for use in the high pressure pump (28), - a second return line section (30.2) configured to direct the gaseous portion of the return fuel to an air intake system (12) of the engine to be fed to the engine with the charge air.
