The lesson from a U.S. Supreme Court ruling earlier this week on pension payouts is clear for working Americans: Make sure your designated beneficiary forms are updated or your pension and retirement funds may not go to your loved ones.

The high court ruled Monday that DuPont Co. was correct to pay some $400,000 in retirement benefits to a deceased worker’s ex-wife, even after she had given up her rights to the pension during their divorce.

When William and Liv Kennedy married, he designated her as the beneficiary to his pension. Nearly 22 years later, they divorced and Liv waived her rights to the retirement money. But William never changed his beneficiary on the retirement account.

Kari Kennedy, his daughter, who was also the administrator of his estate when he died in 2001, sued DuPont successfully in federal court in Texas to recover the money. But a U.S. court of appeals reversed that decision, saying that DuPont pension plan administrators properly followed William Kennedy’s beneficiary designation. The Supreme Court agreed unanimously.

“This is the right decision for the right reasons,” says Rebecca Davis, staff attorney for the Pension Rights Center in Washington, D.C. “A company has to pay out according to what the participant wanted. Maybe he wanted his ex-wife to have his pension and maybe he didn’t. We have no way of knowing. You can’t expect a plan to speculate on what a participant’s wishes were.”

The take-away message, says Mary Ellen Signorille, an attorney for AARP, which filed a friend of the court brief, is simple: Remember to update beneficiary forms whenever a change in your family status takes place. People who are going through divorces should be sure to change beneficiary designations after the divorce is final—even if an ex-spouse waives his or her rights to retirement funds.

“Employee benefits are one of the largest assets in most marriages,” Signorille adds. “It’s important that participants and beneficiaries understand the plan’s requirements when dividing marital assets.”

Carole Fleck is a senior editor at AARP Bulletin.