Venus Williams won 6-3, 6-4 against little sister Serena in the third round of the BNP Paribas Open on Monday night.
For Venus, this is her first victory in the sibling rivalry since 2014.
The two sisters met on the court for the first time since last year's Australian Open final, when a pregnant Serena won her 23rd Grand Slam title.
Venus needed an hour-and-a-half and two match points to secure the victory. Serena ended the match with a forehand failing to find the court, one of her 41 unforced errors.
Serena is still ahead on the head-to-head stats, leading 17-12 overall, although Venus evened their WTA Tour clashes at 7-7.
Away from the actual tennis, a fan spotted a pretty funny thing on TV whilst watching the enticing match.
The provider didn't find it necessary to put a first-name letter on the scoreboard, so the viewers had to wonder who was who.
See the hilarious caption below.
Obviously that led to a few complaints from the fans on Twitter.
Serena, the Williams that lost, looked pretty annoyed after the defeat.
"I really abhor every time we play, but I do enjoy the battle when I'm out there. It's just afterwards I don't like it as much," she said after the match.
It was obvious both were not over the moon, as neither smiled when they greeted after the game. Venus did her usual pirouette, but still didn't release a smile.
A stone-faced Serena was cheered heading out of the court, pointing her right index finger in the air.
This was Serena's first time on the WTA Tour since ending a 14-month absence, during which she married Reddit co-founder Alexis Ohanian, and gave birth to daughter Alexis Jr.
It's unusual to see the sisters meet at such an early stage of a tournament, but this time, 36-year-old Serena was unseeded, and Venus was seeded eighth.
It's good to have them both back at the Indian Wells, after they boycotted the tournament since a racism incident in 2001.
It was 14-year absence before Serena came back in 2015, only to withdraw with a knee injury before her semi-final.
Since that unpleasant time, both of the Williams sisters have been well received by the fans in California.