In this case, the Williamses were up a set and 4-1 before Chan and Huber reeled off five straight games to force a match tie-break, where the Williamses eventually had two match points at 9-7. But this time, Chan and Huber were the ones who won four straight points for a 67(3) 64 119 triumph.
"We never gave up in the match," Chan said. "In the Tokyo final, we were 9-7 up in the final set and we lost the match. Then today it was 7-9 and I told my partner this time we would come back.
"The Williams sisters are the best in the world. We are very happy to win this match."
The victory had to be especially sweet for Huber, who had been 0-7 against the Williams sisters with various partners. Having fallen in the US Open semifinals to eventual champs Andrea Hlavackova and Lucie Hradecka, the Williamses have now lost consecutive matches for the first time since 1998.
Chan and Huber will try for another upset win on Tuesday against World No.1s Sara Errani and Roberta Vinci. No.2 seeds Hsieh Su-Wei and Peng Shuai, who will clinch a spot in the TEB BNP Paribas WTA Championships - Istanbul if they secure the title here, are also in action.