Donald Trump’s aversion to formal briefings leads him to “simply tune out” his National Security Adviser, H.R. McMaster, Axios reports.

A source detailed the president’s preferred style of communication—short and informal. According to Axios, McMaster, a career military man with a penchant for “crisp, linear” and highly-detailed briefings, can not effectively communicate Trump, who “sometimes simply tunes McMaster out,” a source said.

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Axios notes the president ”likes to be discursive and will frequently turn to others or meander into other subjects” during the middle of McMaster’s briefings. He reportedly even once no-so-jokingly asked to other attendees at a meeting, ”can you believe this guy?”

Trump reportedly misses former National Security Adviser Michael Flynn, who was “spontaneous” in his briefings and jived well with the president. Flynn resigned from his role as national s security adviser less than one month after assuming the position after it was revealed he lied about discussing sanctions with Russian ambassador Sergey Kislyak during the transition.