In a gas turbine having a chordal hinge seal between an inner rail of each nozzle segment and an annular axially facing sealing surface of a nozzle support ring, a supplemental seal is disposed between the support ring and inner rail of the nozzle segment. The supplemental seal is formed of a preloaded flexible sheet metal seal having a first margin secured in a linear groove extending in a tangential direction along the inner rail of the nozzle segments with a bent-over edge to form a seal therewith. The opposite second margin has an edge which bears against the axially opposed sealing surface of the nozzle support ring. Sealing pressure against the preloaded flexible seal from a high pressure region maintains the seal between the sealing surfaces of the support ring and segments. The supplemental seal extends tangentially and end edges thereof overlap one another to form a seal between adjacent nozzle segments.