Abstract: A gas flow interrupter for a gas meter, the interrupter comprising a valve member that is movable relative to a valve seat which defines an opening for passing said gas flow, said valve member comprising firstly a membrane having a main surface including a "contact zone" portion that comes into contact with said valve seat when the interrupter is in its closed position, thereby closing said opening by means of the main surface of the valve member, and secondly a part that forms a mechanical support for the membrane and that co-operates with said membrane, wherein the metal part forming a support for the membrane has a continuous leakproof surface bounded by the contact zone so as to close the opening in the event of the membrane failing to provide sealing.