Iowa Gov. Terry Branstad on Monday commuted the mandatory life sentences of 38 convicted killers who committed their crimes as juveniles, a move aimed at ensuring they will spend decades in prison rather than be released earlier because of a U.S. Supreme Court decision.

The governor’s action changes 38 sentences from life without the possibility of parole to life sentences that allow parole only after 60 years.

Branstad said he wanted to keep the inmates from being resentenced, possibly to far more lenient prison terms, in the wake of a Supreme Court decision that barred sentences of life without parole for juveniles.