Unique hue settings of 185 observers under two room lighting conditions were used to evaluate the accuracy of mixed chromatic adaptation transform models of CIECAM02 in terms of unique hue reproduction. The current CIE recommendation for mixed chromatic adaptation ratio produced unsatisfying performance in terms of perceptual hue shifts in CIECAM02. Using our large data set of unique hue data as a benchmark, an optimised parameter is suggested for chromatic adaptation under mixed illumination conditions that produces more accurate results in unique hue reproduction.