A gas supply system of a gas engine or dual fuel engine, having a gas regulating station for supplying the engine in a gas fuel mode of the same with a gaseous fuel of constant gas pressure dependent on a requested engine output, having a double-walled gas line extending from the gas regulating station to cylinders of the engine, which comprises an inner pipe and an outer pipe surrounding the inner pipe at least in sections, wherein in the region of the gas regulating station a gas line extends to the gas regulating station-side end of the double-walled gas line, which is integrated in the at least one gas shut-off valve, wherein this gas line merges into the inner pipe of the double-walled gas line or provides the same, wherein in the region of the gas regulating station at least one vent line with a vent valve integrated in the respective vent line branches off the gas line between the at least one gas shut-off valve and the gas regulating station-side end of the double-walled gas line, wherein in the gas fuel mode the inner pipe of the double-walled gas line, emanating from a gas regulating station-side end of the double-walled gas line can be flowed through by the gaseous fuel in the direction of an engine-side end of the double-walled gas line, having an inert gas purging line and a first shut-off valve assigned to the inert gas purging line, wherein in a purging mode of the engine with opened first shut-off valve, inert gas can be supplied via the inert gas purging line to the outer pipe of the double-walled gas line on the gas regulating station-side end of the double-walled gas line, which flows through the outer pipe in the direction of the engine-side end of the double-walled gas line, there passes into the inner pipe and via the inner pipe flows back in the direction of the gas regulating station-side end of the double-walled gas line, in order to exit from the same, namely in such a manner that with opened vent valve and closed gas shut-off valve the inert gas exiting at the gas regulating station-side end from the double-walled gas line in the purging mode of the engine, can be discharged via the respective vent line. having a gas regulating station for supplying the engine in a gas fuel mode of the same with a gaseous fuel of constant gas pressure dependent on a requested engine output, having a double-walled gas line extending from the gas regulating station to cylinders of the engine, which comprises an inner pipe and an outer pipe surrounding the inner pipe at least in sections, wherein in the region of the gas regulating station a gas line extends to the gas regulating station-side end of the double-walled gas line, which is integrated in the at least one gas shut-off valve, wherein this gas line merges into the inner pipe of the double-walled gas line or provides the same, wherein in the region of the gas regulating station at least one vent line with a vent valve integrated in the respective vent line branches off the gas line between the at least one gas shut-off valve and the gas regulating station-side end of the double-walled gas line, wherein in the gas fuel mode the inner pipe of the double-walled gas line, emanating from a gas regulating station-side end of the double-walled gas line can be flowed through by the gaseous fuel in the direction of an engine-side end of the double-walled gas line, having an inert gas purging line and a first shut-off valve assigned to the inert gas purging line, wherein in a purging mode of the engine with opened first shut-off valve, inert gas can be supplied via the inert gas purging line to the outer pipe of the double-walled gas line on the gas regulating station-side end of the double-walled gas line, which flows through the outer pipe in the direction of the engine-side end of the double-walled gas line, there passes into the inner pipe and via the inner pipe flows back in the direction of the gas regulating station-side end of the double-walled gas line, in order to exit from the same, namely in such a manner that with opened vent valve and closed gas shut-off valve the inert gas exiting at the gas regulating station-side end from the double-walled gas line in the purging mode of the engine, can be discharged via the respective vent line.