Angie Harmon and Sasha Alexander have worked together for five seasons on Rizzoli &Isles, so it’s no surprise that they’re close. Close enough, in fact, that Harmon isn’t afraid to give unsolicited fashion advice to her co-star.

The duo have been friends long enough that they finish each other’s sentences, which left Harmon comfortable enough to call out her friend when she wore a questionable pair of shoes on set.

“We were in rehearsal and I look down in literally the middle of the scene and I’m like, ‘Listen, Maura, you, um, what are those?’ I completely came out of character when I saw her shoes. She’s like, ‘They’re Birkenstocks.’ I’m like, ‘No, those have to go. You can’t wear those ever again. I can’t even rehearse with you right now.’ But Celine just came out with these ‘Birkenstocks’ lined with fur. I went in, bought a pair — not cheap — just to play a joke on her because my favorite thing is to make her laugh. I walked into the set and said, ‘Well, hello. If you’re going to wear Birkenstocks, they need to look like these,'” Harmon said.

The show–which has just been picked up for another season by TNT–was ranked number one in basic cable shows over the summer and stars the friends as crime-fighting partners on the mean streets of Boston.