Credit: Flynet

Taylor Lautner and Taylor Swift have been caught making out!

Too bad it was on the set of their upcoming flick, Valentine's Day.

One of the romantic comedy's costars, Emma Roberts, was on set during the scenes shared by the New Moon star, 17, and the country singer, 19, and she admits they did more than share one on-screen kiss.

"They just had to make out," she told MTV of the daylong shoot. "That's all I saw!"

Roberts -- a self-proclaimed "big Twilight fan" who is "solidly" on Team Jacob -- made sure she was on set when Lautner was, even though she wasn't needed.

"We didn't have scenes together, but I met him on set," she said. "He's a really good guy... It was fun. They were both really cool. I hung out with them a little bit."

Lautner and Swift -- who have both coyly avoided talking about their relationship -- play a high school couple in Valentine's Day, out Feb. 12.

"That movie was a lot of fun," Lautner said at the conference for New Moon last month. "Taylor was great... so I'm excited to go and see that."