In November, an Oklahoma court ordered the Continental Resources chief executive to pay his ex-wife about $1 billion in cash and assets when the couple divorced after a 26-year marriage. The check for $975 million, which Arnall cashed last week, represented the entire balance owed by Hamm according to the court’s decision.

But Arnall has appealed the case in the Oklahoma Supreme Court, claiming that the earlier ruling allowed Hamm to keep the vast majority of a marital estate worth up to $18 billion. Legal experts say it may be more difficult for Arnall to pursue an appeal after accepting the benefits of the trial court’s award.

“I will not dismiss my appeal and do not feel that my right to appeal should be denied because I have accepted, in the interim, a small portion of the estate that we built over more than two decades,” Arnall said in a statement through her lawyers.

Last week, one of Hamm’s lawyers, Craig Box, told Reuters that Arnall’s deposit of the oil man’s check in anOklahoma City bank was likely to end her case. If she continues an appeal, Box said, Hamm will try to have it dismissed on grounds she has already accepted the benefits of the earlier ruling.

The Hamm divorce has been ongoing since 2012 and the November ruling was among the largest ever for U.S. divorces.

Last month, Hamm too had pledged to appeal the decision, after a sharp fall in oil prices cut billions from his personal fortune. The earlier court ruling allowed Hamm to retain his 68 percent stake in Continental.