No organization wants to make the announcement that JPMorgan Chase & Co. had to give when they informed the public that Chairman and CEO Jamie Dimon had to undergo an unplanned heart procedure to fix an acute aortic dissection, according to reports.

There are few risks greater for boards to prepare for than when a CEO suddenly faces a long-term illness or, worse, death. It’s not just a personal blow to members of the board that have worked with the executive, but also one that can thrust the organization into a chaotic search for a replacement. Addressing the potential impact to a business requires the right amount of succession planning.

But most organizations aren’t doing enough. While boards of Fortune 250 companies report that fewer than four people could do the job of their CEO, according to a study by Stanford Business School, 58% do not have emergency succession plans in place, according to a 2016 study by IMD professors Professors Robert Hooijberg and Nancy Lane. The International Journal of Financial Research found that the lack of a clear succession plan for a CEO could lead to an additional $136 million expense, on average, when compared to firms that have an orderly succession in place.

Succession planning doesn’t require giving up on a CEO you believe in. Oscar Munoz, the chairman and chief executive of United Airlines Holdings, suffered a heart attack just over a month into his tenure as CEO in 2015, requiring a heart transplant. United’s patience in his recovery paid off. Since he has returned, Munoz has received praise over his ability to shift the airline to his vision.

It’s important to give your CEO time, but also to plan for the worst. Make sure to outline CEO search roles in advance, including selecting one director to lead the effort, in case of a sudden health concern. “An independent director will need to take the lead in convening special executive sessions to discuss potential succession issues and should know how to call all the independent directors together quickly in case of a crisis,” writes Holly Gregory, a partner at the law firm Sidley Austin, in Practical Law.

Ensure the selected director understands who they will turn to for guidance on issues, such as governance, compliance and media strategy, Gregory continues.

Succession planning should include knowing the candidates for potential replacements, both internally and externally. One strategy to consider is developing a year-round effort to meet with qualified talent. Search firms use strategic introductions to present top talent to companies as a way for boards to craft a plan. These should include non-disclosure agreements, so whispers of a potential CEO don’t emerge from a simple meet-and-greet. These meeting aren’t to hire a CEO today, but to know of candidates who are available so you can have targets to tap in case the health scare requires a permanent replacement.