However the winning penalty sparked controversy from St Mirren boss Gus MacPherson who accused referee Eddie Smith of winking at him after the official had awarded Celtic the spot kick.
MacPherson said: "I thought St Mirren players were outstanding from the first minute to the last and that's all I will talk about.
"The referee was winking at me. He would need to explain why, I don't know whether he was trying to irritate me or not, I don't know. But he'll deny it.
"It's so, so difficult to say what you really feel. We've seen it go on a number of times now and you've just got to bite your tongue.
"It's not going to change anything. We lost the game 1-0 and it was out of our control, and there's nothing we can do about it.
"I actually haven't seen the incident yet but what I've been told by people whom I trust and respect, it was offside and then a free-kick for us.
"From what I've heard there is contact on Haining from Vennegoor of Hesselink.
"But Eddie Smith won't change his mind. He and his observer thought they got it right last season - and that's worrying.
"It's irrelevant to ask if the penalty would have been given for us at the other end, it doesn't matter, it's been given and we get on with it.
"Was it a free-kick? Was he offside? There are a lot of questions to be answered but there's no point in asking the questions, we won't get the answers."
MacPherson also claimed he had been one of several managers that had been singled out at the referees' summer summit at St Andrews.
He said: "When you hear of a referees' meeting with SPL managers up on screens, then you maybe think you will become a target.
"I was one of them. I don't know the context but I would be concerned if we are talking about or targeting individual managers. It's dangerous."