Any provision of this article or Article 4 (commencing with Section 21350) of Chapter 13 imposing as a condition for payment of an allowance to a surviving spouse that he or she have been married to the member for at least one year prior to retirement shall be deemed satisfied if the member was required to retire because of attainment of mandatory retirement age within one year following an amendment to the retirement law or the contracting agency’s contract lowering the mandatory retirement age for his or her category of membership, and the surviving spouse was married to the member on the date of the amendment.