Laura Massaro's title defence ended in the Women's World Squash Championship quarter-finals as she lost to Alison Waters in an all-English battle.
Second seed Massaro, 31, won the first set 14-12, but Waters, the fifth seed, fought back to win the next three 11-2 11-7 11-9 and seal the match in Cairo.
Waters, 30, who plays Raneem El Weleily in the semi-finals, said: "This is a big win for me."
Meanwhile, number one seed Nicol David also progressed to the semi-finals.
Malaysian David, who is the first player to top the world rankings for 100 consecutive months, is looking to extend her all-time record of world titles to eight.
The 31-year-old did not drop a game as she beat Camille Serme 11-9 11-7 13-11 to set up a semi-final against Omneya Abdel Kawy in a repeat of the 2010 world final.
Massaro was hoping to become the first person to win three world titles in a year, having lifted her first title in March before being part of the England squad which won the world team event earlier this month.
But despite some good form in the first set, the 31-year-old struggled to assert her authority, allowing Waters, ranked fifth in the world, to progress to the last four.
Waters, from London, added: "I'm sure we'll have a lot more battles in the future. But I came here to prove to myself what I could do mentally and I'm pretty proud of what I've achieved."