40 ILCS 5/8-140

A "Widow's Prior Service Annuity", shall be credited for the widow of a male present employee for service prior to the effective date, in accordance with The 1921 Act and this Article, payable from and after the death of the employee. The amount so credited shall be improved by interest at the effective rate until the employee retires from service or attains age 65, whichever first occurs.