Credit: Araya Diaz/

Less than a year after director D.J. Caruso set them up, I Am Number Four costars Dianna Agron, 24, and Alex Pettyfer, 20, are engaged, a source tells Although the couple have remained mum on the news, both of their reps claimed to E! News that the report is "not true."

"[Agron] is an amazing woman, and she's got this old school, classic movie-star elegance to her," Pettyfer gushed to Ellen DeGeneres on her show last week. "I'm just very happy in my personal life."

And in a recent Sugar Magazine interview, the Glee star explained why things work with her British beau.

"Alex might see himself as a bad boy, but he's actually very sweet in real life," Agron said. "It's important to have your differences in any relationship. I wouldn't want to be dating a carbon copy of myself. That would just be boring."

Fans can check out the couple's chemistry when I Am Number Four opens in theaters February 18.