(CNN) -- Venus Williams rolled back the clock at the Rogers Cup in Montreal Saturday to claim victory over her younger sister and World No 1. Serena Williams for the first time in five years.
The unseeded Venus lost the first set of the semifinal matchup on a tie break but battled back to win 6-7 (7/2) 6-2 6-3 in just over two hours.
Venus secured what was effectively the match-wining break in the sixth game of the final set before holding her nerve to serve out.
Despite firing down 19 aces, Serena will be left to rue making considerably more unforced errors than her sister, including nine double faults.
"The level of game we played was pretty high," Venus was quoted as saying by the WTA website after the match.
Venus has struggled for form in recent years and has suffered from injury and illness. But she has bounced back in 2014 and already has one WTA title for the year under her belt.
On finding her way back in to the game, she said: "I've been working hard, and more importantly I've been feeling better.
"I hope I can keep some of this control in my life. If I have that control, I can enjoy being on the court, and I can win as well."
Although she came up short on Saturday, Serena still leads the family head to head in competitive matches by 15-11.
The pair have won 26 major singles titles between them (17 for Serena and nine for Venus) and first faced off in the Australian Open in 1998.
Speaking on court after the match, Serena described being disappointed with some of her own play but was happy to see her sister perform so convincingly.
"She was really opening the court well," Serena said. "She (Venus) is such a good mover.
"I think her serve was way more consistent than mine. I had more aces, but she was just serving better.
"Ultimately I think she returned better as well."
Venus will now play either Agnieszka Radwanska or Ekaterina Makarova, who meet in the day's other semi-final.