(CNN) A Michigan lottery winner must share the $38 million windfall with his ex-wife, even though they were in the process of divorcing when he bought the ticket.

Richard Zelasko won an $80 million Mega Millions jackpot in July 2013 -- after taxes and fees his prize was $38,873,628, according to an opinion issued last week by the Michigan Court of Appeals.

The suburban Detroit man and his then-wife, Mary Elizabeth Zelasko, filed for divorce in late 2011. The case had gone to arbitration, and they were waiting for the arbitrator's opinion when Richard Zelasko won the prize.

The couple were married in 2004 and have three children.

The arbitrator ruled that the ticket was part of the couple's marital assets and awarded $15 million to the wife and divided the rest of their assets, according to the opinion. He said that the "marital property includes all property acquired from the date of marriage until the date of entry of the divorce decree," including property acquired during a separation.

The court also cited the arbitrator's opinion that the winning lottery ticket was probably not the first that Richard Zelesko had purchased during the marriage and that "(a)s losses throughout the marriage were incurred jointly, so should winnings be shared jointly."

It's true that Zelasko spent $1 to buy the winning ticket; however, "the dollar spent was arguably marital money and, as such, a joint investment," the arbitrator said.

The appellate court said it found no errors that would require it to change the award.

"It's very difficult to overturn an arbitration," said Michael Robbins, who's represented Richard Zelasko since 2015.

Robbins told CNN that the couple had been separated since 2009.

An attorney for Mary Elizabeth Zelasko told CNN that he would not comment on the case because it is confidential.

The couple's divorce was finalized in 2018.

Robbins said his client can appeal the ruling and is "considering his options."