During his recent benefit concert at Blythedale Children's Hospital in Valhalla, New York, the 31-year-old troubadour spiced up his set by strumming and crooning through fellow Grammy nominee Carey's 1994 single, "All I Want for Christmas Is You," to the delight of hospital staff and juvenile patients alike.

The invitation-only concert, which occurred on December 22, drew about 400 people. Mayer's set also included a duet with Matchbox 20 frontman Rob Thomas on the Ben E. King classic "Stand By Me." Check out the video of Mayer doing Mariah below:

Whoa; that was so hot, it's surprising that a fire didn't break out. Fortunately, even if a blaze did erupt, Mariah would have Mayer covered in return.