“My concern with Trump will be that he inadvertently leaks, because as he speaks extemporaneously, he’ll pull something out of his hat that he heard in a briefing and say it,” said a former senior U.S. intelligence official who has participated in the process of briefing presidential candidates.

Unlike his presumed rival, former Secretary of State Hillary Clinton, who would receive the same briefing if she’s the Democratic Party nominee, Trump has never sat across the table from U.S. intelligence analysts and been given updates on the latest machinations of ISIS, or efforts by foreign governments to penetrate American computer networks. He also has selected a team of largely unknown advisers who might have trouble helping him to contextualize what he might hear and know what questions to ask. (Of course, Trump isn’t under FBI investigation for potentially spilling secrets from his private email server, like his Democratic rival.)

Trump’s improvisational public speaking style, coupled with his penchant for making unverified—and unverifiable—claims, could make for especially tense sessions. Presidential candidates are given their briefings in highly-secured facilities, in part to impress upon them the sensitive nature of what they’re hearing.

“It’s not an unreasonable concern that he’ll talk publicly about what’s supposed to stay in that room,” said another former senior intelligence official.