Twitter’s board of directors hastily approved a poison pill agreement in the wake of Elon Musk’s unsolicited $43 billion takeover bid that surfaced Thursday.

The “limited duration shareholder rights plan” that was unanimously approved by Twitter board late Thursday is  designed to stop any individual or entity from amassing more than a 15% stake in the company by buying shares on the open market.

“The Rights Plan is intended to enable all shareholders to realize the full value of their investment in Twitter. The Rights Plan will reduce the likelihood that any entity, person or group gains control of Twitter through open market accumulation without paying all shareholders an appropriate control premium or without providing the Board sufficient time to make informed judgments and take actions that are in the best interests of shareholders,” the board stated.

In essence, if any entity acquires shares amounting to 15% of the outstanding equity, Twitter will flood the market with new shares.

“In the event that the rights become exercisable due to the triggering ownership threshold being crossed, each right will entitle its holder (other than the person, entity or group triggering the Rights Plan, whose rights will become void and will not be exercisable) to purchase, at the then-current exercise price, additional shares of common stock having a then-current market value of twice the exercise price of the right,” Twitter stated.

The plan will be in force through April 14, 2023.

Musk, the maverick entrepreneur and investor behind Tesla and SpaceX, surprised the business world Thursday with his unsolicited all-cash offer valuing Twitter at $54.20 per share. Musk’s latest headline-making move raised skepticism in investor circles about whether he has the ability to pull off such a transaction.

Musk on Thursday issued a long letter and tweets offering his rationale for taking Twitter private and suggestions for improving the social media giant. “Will endeavor to keep as many shareholders in privatized Twitter as allowed by law,” he opined in a tweet.

Musk’s surprise offer is the latest headache for Twitter CEO Parag Agrawal, who took the reins in November.