Senator and 2020 presidential candidate Elizabeth Warren has responded to criticism from Facebook CEO Mark Zuckerberg over her plans to break up major tech companies. This morning, The Verge published leaked audio of an internal Q&A session with Zuckerberg, including a question on Warren’s plan. “If she gets elected president, then I would bet that we will have a legal challenge, and I would bet that we will win the legal challenge,” he responded. “And does that still suck for us? Yeah. I mean, I don’t want to have a major lawsuit against our own government.”

Warren published a cutting response on Twitter. “What would really ‘suck’ is if we don’t fix a corrupt system that lets giant companies like Facebook engage in illegal anticompetitive practices, stomp on consumer privacy rights, and repeatedly fumble their responsibility to protect our democracy,” she wrote.

Warren didn’t go into specifics about Facebook’s “fumbling” of democracy, but the company has been heavily criticized for indirectly letting political firm Cambridge Analytica access user data as well as failing to curb a Russian misinformation campaign during the 2016 presidential election. It’s already dealing with controversy over how to treat political speech in the upcoming 2020 elections.

Facebook, alongside companies like Google and Amazon, is currently facing multiple antitrust probes. Republican and Democratic politicians have both raised the possibility of spinning off WhatsApp and Instagram into separate companies, but Warren has been one of the most vocal critics of Silicon Valley consolidation — and if she’s elected, she might pose the biggest threat to Zuckerberg’s empire.