Soon, you’ll be able to express that you don’t like something on Facebook.

The social media unicorn is coming, according to Mark Zuckerberg. You’ve asked for it for years and years, and now the company is finally building a dislike button.

Surprised? You should be. For years Zuck and company have resisted the many calls from users to give them a way to express the opposite of the now-most-popular emotion in the world – the like.

In rebuking the idea of a dislike button, Facebook always said it didn’t want to bring that sort of negativity to the site. Zuck also said he didn’t want to institute a reddit-like upvote/downvote system.

Just listen to what former CTO Bret Taylor said about it late last year:

“[The dislike button] came up a lot. In fact even the language of the word like was something we discussed a lot as well. But regarding the dislike button, the main reason is that in the context of the social network, the negativity of that button has a lot of unfortunate consequences.

“I have the feeling that if there were to be a ‘dislike’ button is that you would end up with these really negative social aspects to it. If you want to dislike something, you should probably write a comment, because there’s probably a word for what you want to say … I’m not saying the ‘like’ button isn’t flawed would it be even more complex with a negative sentiment like ‘dislike’.”

And that’s the thing about a dislike button. Zuckerberg doesn’t want a network where people are afraid to post anything because of a fear of negative feedback. Sure would like to post a selfie, but I don’t want to get a bunch of dislikes.

But today in a town hall-style Q&A, he changed his tune.

“I think people have asked about the dislike button for many years. Today is a special day because today is the day I can say we’re working on it and shipping it,” he said.

“What [users] really want is the ability to express empathy. Not every moment is a good moment,” Zuckerberg said.

And that’s true – one use of a dislike button is to show empathy. My poor dog fluffy died! Dislike. Donald Trump said some awful things about Mexicans again. Dislike.

But rest assured, given the opportunity, users will deploy a dislike button in the negative ways that Zuckerberg and company fear.

That’s why you can bet it will differ from the like button – at least in some way. How will it work into news feed rankings (the way the like button does)? Will is be available on all types of posts? Expect a lot of controversy to follow. This should be interesting.