RIO DE JANEIRO (CBSNewYork/AP) — Michael Phelps made up for one of the few losses in his Olympic career.

Now, he’s got an even 20 gold medals.

MORE: Medal Count | Photos From Day 4

Phelps avenged his defeat at the 2012 London Games by winning the 200-meter butterfly on Tuesday night, holding off Japan’s Masato Sakai by a mere four-hundredths of a second.

The victory clearly delighted Phelps, who held up one finger, then sat on a lane rope and egged on the roaring crowd at the Olympic Aquatic Stadium.

He’d had this one marked on his calendar ever since he came out of retirement. Four years ago, Phelps misjudged his finish — gliding a little too long after his final stroke — and was edged at the wall by South African Chad le Clos.

This time, it was Phelps out front — barely — while Le Clos could only manage a fourth-place showing. Hungary’s Tamas Kenderesi claimed the bronze.

He has one more race Tuesday night, anchoring the U.S. team in the 4×200-meter freestyle relay.

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