(Reuters) - A late double bogey by world number one Jason Day helped American Dustin Johnson back up his U.S. Open victory with a win at the WGC-Bridgestone Invitational in Akron, Ohio on Sunday.

Johnson closed with 66 for a six-under total of 274 and a one-shot victory over American Scott Piercy (70).

Australian Day (72) finished three shots behind, equal third with Americans Jordan Spieth (67), Matt Kuchar (66) and Kevin Chappell (67).

Johnson and Day were tied for the lead as Day teed off at the 16th and Johnson played the hole ahead.

Johnson made a 16-foot putt for birdie at the 17th, while Day hit an errant tee shot left. His recovery shot went through the fairway and into the right rough and his third shot found the pond guarding the green, for a double-bogey.

Johnson also hit a wild tee shot left at the 18th for a closing bogey, but it did not stop him from claiming back-to-back wins heading to the British Open at Royal Troon in two weeks.

(Reporting by Tim Wharnsby in Toronto; Editing by Andrew Both)