British number four Dan Evans has beaten 12th seed Grigor Dimitrov 6-4 6-4 to reach the last 16 of the Citi Open in Washington.
The 26-year-old world number 82 had three match points at 5-2 in the second set but Dimitrov saved all three.
The Bulgarian, ranked 40, then broke - but Evans held his nerve when serving for the match for a second time and converted his fifth match point.
He will play either Lukas Lacko or Jack Sock for a place in the quarter-finals.