It is Venus' first victory over Serena since August 2014 at the Rogers Cup in Montreal, and the first matchup where Venus was the higher-ranked player since the sisters met at Bangalore in March 2008.

"I'm just lucky that I've played more matches than her right now,'' Venus said in a postmatch on-court interview. "She just came roaring back. I had chances for the match to be over, but it wasn't.''

It was their earliest meeting since a 17-year-old Venus beat 16-year-old Serena in the second round of the 1998 Australian Open. They played Monday night for the first time since last year's Australian Open final, when a pregnant Serena won her 23rd Grand Slam title.

"I definitely know her well, but she definitely played a little bit better than she normally does,'' Serena said. "She served very consistently. She just did everything great.''

Serena, who was unseeded in the tournament, still leads Venus 17-12 in head-to-head meetings. She played in her first WTA tournament after a 14-month layoff for the birth of her first child.

"It's different, I haven't played in over a year. It's definitely not less disappointing, I wish it was. But then I wouldn't be who I am. ... I just have a long way to go and I look forward to the journey," Serena added.

Venus closed out the 1 ½-hour match on her second match point when Serena's forehand service return sailed long. It was one of Serena's 41 unforced errors, including 17 on the forehand side.

Venus broke Serena at love in the sixth game for a 4-2 lead in the first set. She emphatically closed out the 36-minute set with back-to-back aces that clocked 108 mph and 120 mph.

Venus raced out to leads of 3-0 and 5-2 in the second set. Serena's shot went wide to set up her sister's first match point. But Serena cracked a backhand winner down the line for deuce.

Venus' forehand was long and she double-faulted away the game to make it 5-3. Serena held to trail 5-4 with an ace and a clean winner.

Venus faced two break points in the next game, but got bailed out on Serena's consecutive forehand errors to get to deuce. Venus hung on from there to end their 29th meeting.

"Missing shots that I never miss, and so close,'' Serena said. "At least they're in the margin. I'm getting there. It's not exactly where I want to be, but I'll get there eventually.''

The Indian Wells match was 17 years in the making.

The sisters were supposed to play each other in the desert in 2001. A packed stadium awaited their semifinal but shortly before the match was to begin Venus withdrew with a right knee injury. Serena went on to play Kim Clijsters in the final.

Venus and her father Richard were greeted with boos as they made their way to their seats, with some fans believing Richard had been behind Venus' withdrawal.

Richard Williams said he heard racial slurs from the crowd and he paused to shake his fist at them. Serena was booed throughout the final before she beat Clijsters in three sets for her second title in the desert. After that, the sisters boycotted Indian Wells for 14 years.

Serena came back in 2015 only to withdraw with a knee injury before her semifinal, and Venus followed the next year. Both sisters have been greeted warmly by fans each time they've played here since that turbulent time.

"It never crossed my mind,'' Venus said.

In other action on the women's side, Sloane Stephens remained mired in her post-US Open slump.

Stephens, the 13th seed, lost to No. 20 Daria Kasatkina of Russia 6-4, 6-3, and fell to 2-4 in matches this year.

"I mean, not going to be too down about it," Stephens said. "There's always next week and the week after."

Kasatkina has beaten all four of the current Grand Slam champions in the past year: French Open winner Jelena Ostapenko, Australian Open winner Caroline Wozniacki, Wimbledon winner Garbine Muguruza and now Stephens.

Stephens, who won her first major at Flushing Meadows last fall, lost in the first rounds at the Australian Open and in Sydney before reaching the quarterfinals at Acapulco.

Wozniacki outlasted Aliaksandra Sasnovich of Belarus 6-4, 2-6, 6-3 for her 31st career match win at Indian Wells, where she has played 12 straight years. She won in the desert in 2011 and has been runner-up twice.

The highest-seeded player to lose Monday was No. 4 Elina Svitolina of Ukraine, who was beaten 7-5, 6-3 by 27th-seeded Carla Suarez Navarro of Spain. Also losing was No. 12 Julia Goerges of Germany, 6-3, 6-3 to No. 21 Anastasija Sevastova of Latvia.

No. 7 Caroline Garcia of France beat 26th-seeded Daria Gavrilova of Australia 7-5, 6-4; No. 10 Angelique Kerber of Germany defeated No. 24 Elena Vesnina of Russia 7-5, 6-2; and American Danielle Collins continued her run with a 6-4, 6-4 win over fellow wild card Sofya Zhuk of Russia.

"It definitely feels like a big deal because I have never gone this far in a tournament," Collins said.