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After a slow start with Vafaei taking the first frame, O’Sullivan opened had breaks of 33, 52, 55 and 60 to secure the all-important victory.
Watch O'Sullivan close out victory over Vafaei in style
It was a far from vintage performance from O’Sullivan and he admitted post-match he saw the game as “practice”.
"Pleased to be in the next round," he told Eurosport. "I was just laughing at Hossein - he's so funny. I couldn't stop laughing.
'Stop treading on my shoes mate!' - O'Sullivan on his funniest referee run-ins
“I’ve got my eggs in lots of different baskets so I don’t invest everything in one thing. Each tournament I prioritise differently.
“For me it’s just a bit of practice and in some ways I’m getting punished for winning because I don’t get to do the punditry.”
'It's all just a bit of fun, isn't it?' - O'Sullivan 'just having a laugh'
O'Sullivan will return this evening to face either Mei Xi Wen or Elliot Slessor.
Tom Ford beat Kyren Wilson 4-2 to reach the last 16.
Xiao Guodong claimed a surprise 4-3 victory over Jack Lisowski and has been rewarded with a clash against Mark Selby, who beat Matthew Selt 4-2.
17-year-old Si Jiahui impressed again by thrashing Chinese compatriot Zhou Yuelong 4-0.