In an axial flow turbine, such as an exhaust gas turbine, in order to prevent the driving gas from escaping through the slits (9) formed in an outer nozzle ring (8) of integral type construction, which divide said ring into several segments so as to facilitate differential thermal expansion, and thus by-passing the regular flow of the gas through the nozzle structure, filler metals (15) are located in the slits. Preferably, the radial depth of the filler metals is shorter than the slits, and they are fixed e.g. by fixing bolts (17) and tongues (16) provided on the filler metals, so as not to protrude beyond the inner diameter of the outer nozzle ring.