Can a judge set aside an unauthorized sentence and replace it with a proper sentence?

Respondent contends that the trial court erred by ordering that the five-year sentences on the two prior convictions run concurrent with each other. He correctly points out that this court has the authority to set aside an unauthorized sentence and impose a proper sentence in its place, "even though it is more severe than the original unauthorized pronouncement." (People v. Serrato (1973) 9 Cal.3d 753, 764, 109 Cal.Rptr. 65, 512 P.2d 289, disapproved on other grounds in People v. Fosselman (1983) 33 Cal.3d 572, 583, fn. 1, 189 Cal.Rptr. 855, 659 P.2d 1144.)