The invention relates to a gas metering valve (1) for a dual fuel engine (17), which has a displaceable closing body (6) which, in a position of resting against a valve seat (5), closes the gas metering valve (1) and, in a position of being lifted off from the valve seat (5), opens the gas metering valve (1). The gas metering valve (1) is actuatable in a gas operating mode, in which the gas metering valve (1) meters combustion gas via a gas channel (13) into an intake manifold (15) of the dual fuel engine (17), and in a liquid fuel operating mode, in which the gas metering valve (1) remains sealingly closed against the pressure prevalent in the intake manifold (15). The valve seat (5) is movably situated along a valve seat guide (4), the valve seat (5), owing to the combustion gas pressure in the gas channel (13), in the gas operating mode being pressed away from the closing body (6) against a stop (20) in the gas metering valve (1) and is kept in its operating position, and the valve seat (5) in the liquid fuel operating mode being sealingly pressed by the pressure from the intake manifold (15) against the closing body (6).