The compositional dependence of the yield strength σy has been studied for a series of polycrystalline (AuNiPdPt)1−xCux alloys by means of compression tests. σy is found to decrease linearly with increasing Cu concentration. This behaviour is in contradiction to the generalised theory for solid solution strengthening in concentrated solid solutions provided by Varvenne et al. [1]. A breakdown of the scaling behaviour is found as σy should be non-linear and slightly increasing when modifying the composition from AuNiPdPt to AuCuNiPdPt