40 ILCS 5/6-143.2

If any widow (1) receives a widow's annuity from the Fund, and (2) after December 31, 1989 marries a fireman who is a participant in this Fund, and (3) the fireman dies and a second widow's annuity thereby becomes payable, then the first widow's annuity shall be cancelled at the time the widow accepts any payment of the second widow's annuity. Any refund due because of the cancelled annuity shall be paid to the widow.