The color-appearance model CIECAM02 has several problems. which can result in mathematical instabilities, due to the position of the chromatic-adaptation primaries relative to the spectrum locus and to the presumed physiological cone primaries. To keep a corresponding (adapted) color within the positive gamut given by the chromatic adaptation primaries, the gamut must he within the cone primary octant. To contain adapted colors within the positive cone-primary octan, it suffices to truncate the action of adaptation at the boundary of that octant. Such modifications may be needed to avoid the mathematical problems in CIECAM02. (C) 2008 Wiley Periodicals. Inc.