Wanderers have had a couple of other chances throughout the match, but have failed to test the Bristol goalkeeper.
The away side had the perfect start and were ahead within 95 seconds. Darren Pratley raced down the left before firing the ball across the box where it hit Fontaine and went in.
It could have been two a minute later, when Chris Eagles found space 30 yards out but his effort narrowly missed the crossbar.
Adam Bogdan reacted well just before half time to deny Steven Davies and ensured that Wanderers went in ahead at the break.