The I Want It That Way hitmakers are in the midst of their new Sin City residency at the Axis venue in Planet Hollywood, and they decided to invite Lance to perform with them.

The former 'N Sync bandmember was only happy to oblige, and they teamed up for a rendition of Backstreet Boys' ballad Shape of My Heart.

"We really showed @lancebass the shape of our hearts tonight," the group posted on Instagram after the show. "Thanks for coming by #BSBVegas, brother!"

Lance, whose husband Michael Turchin was in the audience cheering the singers on, also celebrated the stage return with a photo of the stars in action, and simply captioned it, "#BSB."

Bass isn't the only 'N Sync member to check out the Backstreet Boys' residency gig - Joey Fatone also enjoyed the show earlier this month (Mar17).