Abstract In a recent paper, Canuto et al. made a crucial contribution to modeling mixing in stably stratified flows by discovering that a modification to one of the closure constants can push the critical gradient Richardson number RiCR, beyond which turbulence is extinguished, to infinity. In this note, following their approach, the Kantha model is modified to yield a value of infinity for RiCR. The results are in good agreement with both the Canuto et al. results and the data presented in their paper.