Briton Kyle Edmund came through a tough test to beat Filip Krajinovic 7-5 6-3 in the Shanghai Masters first round.
Edmund was 4-2 and break point down in the first set when the umpire allowed a late challenge to a line call which went in his favour.
He took the game before levelling at 4-4 and went on to take the opening set.
World number 14 Edmund eventually beat the world number 35 in one hour 31 minutes and will play Italian Andres Seppi in the next round.
Elsewhere, Wimbledon and US Open champion Novak Djokovic, who was given a bye into the second round, beat Frenchman Jeremy Chardy 6-3 7-5.
World number three Djokovic had not lost to 41st-ranked Chardy in their previous 11 meetings and rarely looked like suffering his first defeat against him.