In a nonreturn valve having a tubular body, which can be installed in a vertical section of an exhaust line, a valve seat, formed within the tubular body, for at least one float, and at least one circumferential groove, which is open in the downstream direction, the intention is to make available a solution by means of which it is possible to provide a nonreturn valve that is simple, advantageous in terms of production engineering and has a particularly high performance, and to do so in a way which is simple in terms of design and is economical. This is achieved by virtue of the fact that the circumferential rim of the at least one float projects radially over the radially inner circumferential wall section and has an axial lip facing upstream, which extends into the circumferential groove in the axial direction when the at least one float is resting on the valve seat.