Sue Ann Hamm thinks a $1 billion divorce settlement is not enough.

The ex-wife of Oklahoma oil magnate Harold Hamm says she plans to appeal the judgment on “grounds that it grossly undervalues the marital wealth she is entitled to,” according to NBC News.

Sue Ann was awarded cash and assets worth more than $1 billion in the couple’s divorce this week by Oklahoma County Court Judge Howard Haralson, but is unhappy with a ruling that allows her ex, who is believed to own more oil than any other American, to keep nearly all of an estimated $18 billion rise in his Continental Resources shares during their 26-year marriage.

“Sue Ann is disappointed in the outcome of this case. She dedicated 25 years as Harold’s faithful partner in family and business,” her attorney Ron Barber told Reuters. “She plans to appeal the court’s decision.”

When is a $1 billion divorce payout "a huge win"? When you're oil magnate Harold Hamm. http://t.co/emLjiuV0Rr pic.twitter.com/kW66ZaQAzt

— Dallas Morning News (@dallasnews) November 11, 2014

The Hamm v. Hamm divorce judgment is one of the largest in U.S. history, but the award to Sue Ann is a small fraction of the wealth Haralson allowed Harold Hamm to keep.

Judge orders oil magnate to pay nearly $1 billion in divorce judgment http://t.co/1tyH5H4CMX pic.twitter.com/1p6P0zHnBl

— WPTV (@WPTV) November 11, 2014

The CEO holds more than 68 percent of Continental’s stock, a stake valued at around $13.5 billion today.

Ex-wife of Harold Hamm: $1 billion isn't enough » http://t.co/Z2S72gUkgf pic.twitter.com/AWUh17AgHb

— CNBC (@CNBC) November 15, 2014

The Hamms had no prenuptial agreement, and the filing by Sue Ann claims her husband was unfaithful to her.

Hamm, who was the 13th child of sharecroppers, became Oklahoma’s richest person when Continental’s share value increased by around 400-fold.