Former U.S. Ambassador to the United Nations John Bolton, President Trump’s pick to be his new national security adviser, on Thursday night condemned leaks from the White House as “completely unacceptable.”

During an appearance on Fox News, Bolton referenced a Washington Post report that Trump’s national security team informed him not to congratulate Russian President Vladimir Putin during a phone call earlier in the week. 

The Post report, which said that advisers in briefing materials warned the president “DO NOT CONGRATULATE,” came after Trump told reporters he congratulated Putin on his reelection. The leak reportedly infuriated Trump and his chief of staff John Kelly.

“When I read about the leak of the note and the subject, I was outraged by it,” Bolton said Thursday evening on Fox News.

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“You cannot conduct diplomacy, you cannot expect other foreign leaders to be candid and open in their conversations with the president if some munchkin in the executive branch decides they’re going to leak the talking points or the transcript or any other aspect of it,” Bolton continued.

“And I think this is really a terrible reflection on the individual or individuals who did this. They should be ashamed of themselves,” he continued. “And I think whether you’re a Republican or a Democrat, a liberal or a conservative, there ought to be unity on this point that leaking o that sort is simply unacceptable.”

Trump tweeted earlier in the evening that Bolton, the hawkish former Bush administration official, will take over for national security adviser H.R. McMaster on April 9. Bolton, who was seen visiting the White House on Thursday, will be Trump’s third national security adviser.