Crystal Harris, Hugh Hefner Call Off Wedding

They don't?

Hugh Hefner and Crystal Harris have called off their wedding.

"The wedding is off," Hefner, 85, tweeted Tuesday. "Crystal has had a change of heart."

After getting engaged on Christmas Eve last year, the Playboy founder and Playmate reportedly had an argument over the weekend; according to TMZ, Harris moved out of the Playboy mansion and canceled Saturday's nuptials.

UPDATE: Harris' rep, Michael Blakey, "spoke to Crystal earlier this morning and she had shared the sad news with me," he tells Us Weekly. "The breakup was amicable. Crystal will now be focusing on her music career and her new single 'Club Queen,' which was released today."

Prior to Hefner's Twitter confirmation, Harris hinted: "There are two mistakes one can make along the road to truth...not going all the way, and not starting."

It would have been the third marriage for Hefner, who four kids (ages 58, 55, 10 and 9) with his first two wives. He and Miss December 2009 Harris began dating in January 2009; he proposed with a 3 1/2 carat ring worth an estimated $90,000.

Back in April, Hefner told Us he was "excited" wed his latest love. "Everything in place," he said. "She's wonderful and she's done a really terrific job so far with all the planning. She is the one for me!"

The couple had planned to host 300 guests (who were instructed to donate to charities in lieu of gifts) at the Playboy Mansion on June 18 for their big day.