Canadian teen Summer McIntosh clocked a meet-record 3 minutes 59.42 seconds to win the 400m freestyle at the U.S. Open ahead of American distance great Katie Ledecky.

McIntosh, a four-time world champion, handed Ledecky her first defeat in the event in a U.S. pool in 11 years, seven-time Olympic gold medalist Ledecky taking second in 4:02.38.

McIntosh held the 400m free world record for three months last year. But at the World Championships in Fukuoka, she finished a disappointing fourth as Australian Ariana Titmus regained the world record in winning gold ahead of Ledecky.