Hammad Miah beat Judd Trump on the final black to seal a major upset in the second round of the British Open in Cheltenham.
Each player fired two centuries in a high-quality contest but it was the world number 113 who prevailed in an edgy decider to wrap up a career-best 4-3 win.
Fergal O'Brien fought back after losing the opening frame to beat Noppon Saengkham 4-2. The 31-year-old Thai is ranked 23rd in the world, 80 places ahead of the Dubliner.
O'Brien will next face Matthew Stevens, who won a rematch of the 2000 Masters final 4-3 against Ken Doherty.
The Dubliner went 3-1 up but Stevens hit breaks of 99, 99 and 70 to win the remaining three frames without conceding a point.
Crucible semi-finalist Si Jiahui was back in scintillating form as he reeled off four frames in a row to beat Neil Robertson 4-1.
The former world champion took the first frame with a break of 59 but got few further chances as the Chinese player moved to the brink of victory and finished things off with a break of 107.
Elsewhere, Mark Williams overcame Stephen Maguire 4-2 while other winners included David Gilbert, Hossein Vafaei and Ali Carter.