Heidi Montag is planning for baby after husband Spencer Pratt had a "change of heart."

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Earlier this year, Montag and Pratt, who starred on MTV's The Hills for four years, signed on to appear on WEtv's Marriage Boot Camp. On the show, the couple will address their marital issues, which stem from Montag's desire to have a child, and Pratt's desire to wait. Although the series has yet to air, the couple have already come to an agreement.

“Spencer promised me a baby by 29,” Montag, who turned 28 in September, revealed to Life & Style on Wednesday. “Last year, while we filmed an E! special, he told me, ‘I don’t want to have kids,’ and I started crying. I told him I couldn’t bear the thought of never becoming a mom. So when he saw how important it was to me, he had a change of heart!”

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Montag and Pratt became engaged in May 2007 after meeting in Los Angeles, where Montag was filming The Hills with longtime friend Lauren Conrad. On Nov. 20, 2008, the couple eloped in Mexico as cameras rolled for the show's fourth season. The following year, Montag and Pratt held their official ceremony in Pasadena, Calif.

Earlier this month, the couple celebrated their wedding anniversary. ''Happy 6 year Anniversary!" Montag wrote to Pratt. "Thank you for the best 8 years of my life, 6 married! My heart, my soul, my love! So excited for the next year and all the ones to come! This has been the best yet!''

In a press release for the WEtv series, via Us Weekly, it was noted Montag "desperately wants [kids] now, while Spencer is more interested in going out and having fun."

Marriage Boot Camp returns to WEtv early next year and also includes Real Housewives of New York star Aviva Drescher and her husband Reid, Bad Girls Club's Natalie Nunn and her husband Jacob Payne, Survivor: Blood vs. Water's Tyson Apostol and Rachel Foulger, and R&B Divas' Syleena Johnson and her husband Kiwane Garris.