San Francisco (CNN Business) Keeping Mark Zuckerberg safe is expensive.

Facebook paid its CEO an additional $13 million for his personal security and travel costs in 2018, according to a proxy filing on Friday. That included a new $10 million pre-tax allowance for additional security costs such as security guards, equipment, services and residential improvements.

"He is synonymous with Facebook and, as a result, negative sentiment regarding our company is directly associated with, and often transferred to, Mr. Zuckerberg," said the filing.

Like many wealthy CEOs, Zuckerberg receives an official salary of $1 a year. He also did not receive bonuses or stock awards in 2018. However, Zuckerberg's total compensation jumped from $9.1 million in 2017 to $22.6 million in 2018 in order to cover the increase in security costs for the high-profile CEO.

Facebook's FB The increase is partially the result of specific threats against Zuckerberg andhigh visibility, according to the company.

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