MELBOURNE, Australia (AP)—Venus Williams is a much better doubles partner for her sister Serena than she is a keeper of the score.

The Williams sisters won their fourth Australian Open doubles title on Friday, beating Cara Black and Liezel Huber 6-4, 6-3 in the final at Rod Laver Arena.

At the end, Venus couldn't figure out why Serena was so excited about what she thought was a game point. And Serena was perplexed why Venus was so subdued on match point.

The problem: Venus had lost track of the score.

The sisters, sitting in front of their newly won silverware in a news conference, couldn't contain their laughter when asked about the comical finish to the match.

I actually didn't know the score, I thought that it was 5-2,'' Venus said.I really don't know how I lost track. So I was confused, but I guess that's just focus.

``I thought, she's really happy about this break. I thought, 'Wow, I've never seen her this happy'. But I'll go with it.''

Serena was happy, and confused.

``Yeah, I thought, 'OK, this is exciting. We defended our title' and she was like, 'What's going on?' I'm like, 'The match is over. We're done now.' It was funny.''

Venus said not knowing they were one game away from clinching the match might have helped.

I guess it's easier to hold at 3-2 instead of 4-3. I thought it was break point,'' she said.I didn't know it was match. I need to play all my matches like this without knowing the score. I think it would help.''

The sisters broke Huber's service to open the second set and won the match when they again broke Huber, clinching it on a winning reflex volley by Serena. They high-fived each other at the side of the court after the win.

The Williams sisters won the Australian title for the first time in 2001 and added championships in 2003 and last year. Black, of Zimbabwe, and Huber, a South African-born American citizen, won the Australian Open doubles title in 2007 and were the top-seeded team in the tournament this year.

``I have to congratulate Venus and Serena for a great tournament - you guys are too good,'' Black said.

It was the 11th time the Williams sisters have combined for a Grand Slam doubles title.

Serena has 11 singles majors, also, and is hoping for a 12th in the Australian Open final on Saturday against Justine Henin.

Venus Williams has also won a mixed doubles title at the Australian Open - in 1998 with fellow American Jason Gimelstob. Serena Williams was a losing finalist in mixed doubles here with Max Mirnyi of Belarus in 1999.

Black is still in this year's mixed doubles tournament, playing the semifinals later with Leander Paes of India against Lisa Raymond of the U.S. and Wesley Moodie of South Africa. Paes and Black are the top-seeded team.