British number one Dan Evans produced a superb fightback to beat third seed Karen Khachanov 3-6 7-6 (9-7) 6-4 and reach the European Open semi-finals.
Evans, 30, faced match point in the second set but went on to take the tie-break after a hotly disputed line call.
Early in the deciding set he broke Russian world number 17 Khachanov, before completing victory in two hours 40 minutes.
Evans will face France's Ugo Humbert in the last four in Antwerp on Saturday.
On Saturday, Khachanov said he spoke to the umpire Adel Nour after the match and claimed the official apologised for "the mistakes he made".