Appellant was defendant in a negligence action. He appeals from a verdict and judgment for the plaintiff. The only assignment of error is that in his charge on contributory negligence the trial judge used the permissive “may” rather than the mandatory “must” in instructing the jury on whether they should return a verdict for the defendant if they found the plaintiff contributorily negligent.

Appellant concedes that our decision in Layton v. Rocha, 90 Ariz. 369, 368 P.2d 444 is controlling on this point, but asks us to reconsider and overrule that decision. We are of the opinion that our decision in Lay-ton v. Rocha, supra, was correct, adequately explained the reason for the rule, and we are disposed neither to overrule nor to enlarge on the decision in that case.

Affirmed.