Jennifer Aniston: Proposal Was 'a Very Covert Operation'

"It's hard to pull one over on me," the star says of her surprise engagement

Jason Thomas/FilmMagic

Jennifer Aniston’s engagement ring might have caused quite a stir among fans, but no one is more enamored with the shiny new sparkler than the bride-to-be.

“I was impressed,” she tells PEOPLE of fiancé Justin Theroux‘s final choice. “I had no idea, and I had no idea what I wanted. He just knows what I like.”

Theroux “worked with the girls that I have worked with for years and years and years, so he kind of was picking the specialists’ brains,” Aniston shares. “He kept it within a very small circle of people. It was one of the sneakiest jobs I’ve ever seen, actually.”

And that left the actress, who is the new face and co-owner of Living Proof hair products, doubly impressed.

“It’s hard to pull one over on me,” she says, “where I’m not like, ‘Hmm, you’re acting really strange.’ It was … a very covert operation.” For more of our exclusive interview with Aniston, pick up the latest issue of PEOPLE, on newsstands now.

–Reporting by Julie Jordan

PHOTOS: SEE 13 MORE GORGEOUS STAR ENGAGEMENT RINGS