A group of Kroger employees and retirees is suing an Illinois-based pension fund, claiming their retirement money has been mismanaged.

The lawsuit involves an underfunded pension plan called Central States, Southeast and Southwest Areas Pension Fund that holds about 5,000 current and retired Kroger Co. (NYSE: KR) employees’ retirement funds, according to the complaint filed in U.S. District Court in Illinois. The outside plan has lost assets over the years as fewer members contribute and thanks to investment losses. Kroger employees want out of the plan.

The 11 employees and retirees who filed the lawsuit call the pension plan “massively underfunded” and say it’s projected to be insolvent by 2026, according to the lawsuit. The plan has $17.8 billion in assets and $35 billion in promised investments.

The plaintiffs in the case live in Indiana, Michigan and Kansas. They worked at Kroger for decades. Many are retired but have gotten jobs to make up for lost pension benefits or are expecting to get jobs during their retirement.