Bernard Madoff, who was convicted of running the largest Ponzi scheme in U.S. history, has asked President Donald Trump to shorten his 150-year prison sentence.

The 81-year-old convict filed a clemency request with the Department of Justice. It is not clear exactly when the request was made.

Madoff took around $20 billion in principal from investors, telling them he was investing the money for them. He made up financial statements that purported to show them earning excellent returns when in fact he was using the money to pay for his own lavish lifestyle and pay some investor withdrawals. Almost no trading or investing actually took place, prosecutors showed.

Madoff is currently serving out his sentence in federal prison in Butner, North Carolina.

Madoff’s younger brother, Peter Madoff, pleaded guilty in 2012 to falsifying records in connection with the Ponzi scheme. He was sentenced to 10 years in prison and is due to be released in 2020.

Madoff’s sons, Mark and Andrew, both died in the years since the scheme unraveled. Mark Madoff hanged himself in 2010. Andrew died of cancer in 2014. Neither were charged with a crime, although their estates have agreed to pay millions to the victims of the Ponzi scheme.

Madoff’s wife, Ruth, has agreed to surrender all of her assets to a fund to pay victims upon her death. She also has not been charged in connection with the fraud.

There are still mysteries about Madoff’s scheme, particularly about why he engaged in such widespread fraud and how long he had been cheating his clients. After his conviction, he was initially contrite but later blamed some of his early investors for pressuring him to produce very high returns. He claimed he started his firm with money earned while lifeguarding on New York City beaches, but that is unlikely.

The clemency request was first reported by CNBC.

“I’m confident that the career [Justice Department] attorneys responsible for evaluating such requests will reject it out of hand,” Marc Litt, who was the lead federal prosecutor in the criminal case against Madoff, told CNBC on Wednesday.