JOHANNESBURG (AP) — South Africa’s former President Nelson Mandela underwent a successful surgery to remove gallstones Saturday, the nation’s presidency said, as the 94-year-old anti-apartheid icon is still recovering from a lung infection.

Doctors treating Mandela waited to perform the endoscopic surgery as they wanted to first attend to his lung ailment, presidential spokesman Mac Maharaj said in a statement. Mandela has been hospitalized since Dec. 8.