Facebook has a breast phobia. Anyone who’s attempted to post art, breastfeeding photographs, and even photos that resemble breasts but are not actually breasts, only to have them removed, know this.

We’ve covered Facebook’s wonky content-removal system plenty of times. Here’s how the script usually reads: Someone posts a photo on Facebook that depicts breasts in a non-pornographic setting; Facebook yanks the photo; People protest; Facebook reinstates the photo, saying that it was removed in error.

Considering Facebook has billions upon billions of pieces of content to moderate at all times and that they outsource a lot of it, it’s inevitable that they’re going to make some mistakes. That’s not an excuse for Facebook’s content-removal screwups, mind you, just an explanation.

This latest episode in the series is a bit different, however. A public outcry, complete with a successful petition, not only forced Facebook to backtrack on the content-removal, but also forced them to clarify a specific policy geared toward a specific type of photo:

The post-mastectomy photo.

Here’s the story. It all begins with a Facebook page for The SCAR Project, an alternative breast cancer awareness initiative that “puts a raw, unflinching face on early onset breast cancer” with a series of large-scale portraits of young cancer survivors.

“Breast Cancer Is Not A Pink Ribbon,” they say.

The Facebook page, unsurprisingly, contains plenty of these portraits featuring nude women, post-mastectomy. A few weeks ago, Facebook began removing many of these photos, much to the chagrin of the project’s admins. They initiated an online petition on Change.org that has received over 21,000 signatures.

This prompted Facebook to clarify their position on mastectomy photos – Yes, they allow them. Here’s what Facebook has to say in a new Help Center post:

Yes. We agree that undergoing a mastectomy is a life-changing experience and that sharing photos can help raise awareness about breast cancer and support the men and women facing a diagnosis, undergoing treatment, or living with the scars of cancer. The vast majority of these kinds of photos are compliant with our policies.

However, photos with fully exposed breasts, particularly if they’re unaffected by surgery, do violate Facebook’s Terms. These policies are based on the same standards which apply to television and print media, and that govern sites with a significant number of young people.

Another statement from Facebook outlines what I said before – that Facebook sometimes screws up. Plain and simple.

“We have long allowed mastectomy photos to be shared on Facebook, as well as educational and scientific photos of the human body and photos of women breastfeeding,” Facebook said in a prepared statement. “We only review or remove photos after they have been reported to us by people who see the images in their News Feeds or otherwise discover them. On occasion, we may remove a photo showing mastectomy scarring either by mistake, as our teams review millions of pieces of content daily, or because a photo has violated our terms for other reasons.”

Facebook’s content moderation system is always going to be a headache. It’s the nature of the beast. But small movements like this show that if you bring it to their attention and drive enough support, they’ll most likely listen.