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 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 of the inner rail. The sheet metal seal has a flexible margin which is preloaded and bears against the annular sealing surface of the nozzle support ring. The bracket is bolted or welded to the inner rail with the sheet metal seal therebetween inhibiting or precluding leakage past the back side of the supplemental seal.