Not so fast Elon! Last Friday, Twitter’s (TWTR) board of directors voted unanimously on a move to block Elon Musk’s proposed takeover of the social media company.

Should Musk attempt to purchase at least 15% of the company, all of Twitter’s other shareholders (excluding Musk) would be granted the right to purchase additional shares at a heavily discounted price, thus diluting the value of shares and Musk’s ownership.

The strategy, which is formally known as a “shareholder rights plan” and informally as a “poison pill”, is commonly used by corporations to stop hostile takeover bids.

Musk isn’t the only one with a sudden interest in buying Twitter though. According to sources, private equity firm Thomas Bravo LP is putting together an acquisition bid for Twitter to rival Musk’s $43b bid.