President Donald Trump said Thursday that he would nominate outgoing national security adviser Mike Waltz to be the U.S. ambassador to the United Nations. Waltz, a former congressman from Florida, has been on shaky ground with Trump since March after he inadvertently added a journalist to a private chat on the messaging app Signal with other top national security officials to discuss military strikes in Yemen.

Mike Waltz just can’t seem to quit Signal. President Donald Trump’s outgoing national security adviser, the subject of fevered speculation Thursday about his future, was photographed looking at his phone under the table during Wednesday’s Cabinet meeting.