Iga Swiatek started her French Open title defence with a straight-sets win over her good friend Kaja Juvan in the first round on her 20th birthday on Monday.
The Pole, who powered to a surprise triumph last year at Roland Garros, won 6-0, 7-5 against her Slovenian opponent.
"You never know what's going to happen and I've never been a defending champion, even in the smallest tournaments, so I didn't know what to expect," said Swiatek, who was presented with flowers on court after the match for her birthday.
Swiatek will face either Sweden's Rebecca Peterson or American Shelby Rogers in the second round.
The first set was the eighth seed's third straight bagel after thumping Karolina Pliskova 6-0, 6-0 in the Italian Open final earlier this month, which saw her break into the world's top 10.
Juvan put up much more of a fight in the second set, though, battling back from 3-1 down before missing two break points in the 11th game.
But her resistance ended shortly afterwards, as Swiatek came back from 40-0 down in the next game and secured victory on her fourth match point in the sunshine on Court Philippe Chatrier.
"In the second set it was really hard, she didn't give me any birthday gifts," added Swiatek. "So I'm really happy I could win those important points."