In a gas turbine having a chordal hinge seal between an inner rail (52) of each nozzle segment and an annular axially facing sealing surface (54) of a nozzle support ring (44), a supplemental seal (70) is disposed between the support ring and inner rail of the nozzle segment on a high pressure side of the chordal hinge seal. The supplemental seal includes a sheet metal seal supported by a bracket secured to the back side and radial inner surfaces (79, 80) of the inner rail. The sheet metal seal has a flexible margin (86) which is preloaded and bears against the annular sealing surface of the nozzle support ring. The bracket is bolted (96) or welded to the inner rail with the sheet metal seal therebetween inhibiting or precluding leakage past the back side of the supplemental seal.