Greg Lippmann’s LibreMax Capital gained 20.8% last year as hedge funds focused on mortgage debt outperformed rivals.

LibreMax’s main fund rose 0.94% last month, according to a person familiar with its returns, who declined to be identified because the information is private.

The firm had about half of its bullish bets on U.S. home-loan bonds without government backing as of Sept. 30 and also began wagering on commercial-mortgage securities in 2012, according to a November letter to investors.