A reaction cuvette having anti-wicking wall fillets that inhibit liquid wicking along an interior wall surface so that the reaction cuvette may be used in a cuvette-rewashing system in an automated analyzer and not be adversely affected by any reagent contaminants remaining from assays previously performed in said reaction cuvette. The anti-wicking wall fillets comprise a curvilinear taper extending from an open top downwards into the cuvette to form a rounded concave blend between the cuvette's front and back walls and side walls.