12/26/2012 at 02:10 PM EST
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."