She describes the picture of her boyfriend as "Santa Baby" on Twitter

By Marla Lehner
Updated December 26, 2012 02:10 PM
Courtesy Katy Perry

Ho, ho, ho!

Katy Perry celebrated Christmas this year with her boyfriend John Mayer – and she posted a picture on Twitter to prove it.

On Christmas Day, Perry, 28, shared a photo of Mayer dressed in a Santa suit and giving a seductive look, captioned, “Santa Baby.”

The two lovebirds went to her home for the holidays where they spent the big day with her family, a source tells PEOPLE.

“They’re happy together and with her family for the holidays,” says the source. “John really likes getting to know Katy’s family better.”

And, according to the source, the two singers – whose relationship was off and on in the beginning, but has been steady for the last several months – are getting serious about each other.

“They’ve spent a lot of time together and really enjoy each other’s company,” says the source. “John is entirely focused on Katy.”