Marco Fu held his nerve to upset 15th seed Alan McManus 13-7 and reach the last eight for the first time in his career.
The qualifier from Hong Kong triumphed over the out-of-form Scot in a match full of safety-dominated frames.
With Fu leading 10-6 overnight, McManus soon reduced the deficit, but a break of 75 put Fu within sight of victory.
The world number 27 then rattled in a 57 break, and when McManus missed a straightforward brown in frame 20, Fu took full advantage to clinch the match.