705 ILCS 5/15

Whenever any judgment shall have been rendered in the supreme court which, upon further consideration, is found to have been erroneously entered up, the judges thereof are authorized, during vacation, to change the same without ordering a rehearing thereof, by entering a proper judgment in said cause; and in case a mandate shall have been issued in such cause, the judges may recall the same, and, by order of any of the judges, all proceedings taken by reason of such mandate shall be vacated and set aside: Provided, that all such judgments shall be corrected within six months from the adjournment of the term at which they may have been rendered.