The chief judge of the U.S. District Court of Massachusetts has decided to become a senior judge next year, creating a vacancy that will give the district court a new, additional judge.

Mark Wolf informed President Barack Obama of his decision Tuesday. Wolf said he will continue to provide “substantial service,” though senior judges have a lighter caseload.

Wolf was nominated to the court by President Ronald Reagan in 1985.

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His seven-year term as chief judge ends on Dec. 31. Wolf said he will be 66 by Jan. 1, when he will begin his status as a senior judge.

Wolf recently issued a landmark ruling, ordering the state Department of Correction to provide sex-reassignment surgery for a convicted murderer.

Judge Patti Saris will become chief judge when Wolf’s term ends.