An aqueous binder composition having a reduced tendency to yellow containingA) 20 to 95 wt-% of a water-dilutable organic polyol component that is present in the form of an aqueous solution or dispersion, contains one or more polymer-modified polyester resins which contain carboxylate groups and hydroxyl groups and has been prepared by the polymerization of olefinically unsaturated monomers in the presence of an unsaturated polyester resin that is copolymerized with the monomers andB) 5 to 80 wt-% of at least one heat-activatable cross-linking resin,wherein the percentages are based on the solids contents of components A) and B) and add up to 100%; and their use in heat-curable coating compositions.