A career diplomat with nearly three decades of service under his belt said a Trump appointee canned him for a simple sin: He talked about Obama.

Lewis Lukens, the former deputy chief of mission at the U.S. embassy in London, recounted his October 2018 firing a GQ magazine article published Tuesday. It was an unceremonious end to nearly 30 years in the foreign service, including stints as the U.S. ambassador to Senegal and Guinea-Bissau and the acting ambassador to the United Kingdom.

Lukens said that a quick anecdote in a speech — he told U.K. students about former President Barack Obama deftly handling a tough media question about LGBT rights in Senegal — was all it took to derail his career. President Donald Trump had recently attacked prominent British leaders — chiefly the then-Prime Minister Theresa May and London Mayor Sadiq Khan — and in his story, Lukens emphasized that civil disagreement between leaders was possible.

Just a week later, he says, he was fired by U.S. ambassador to the U.K. Woody Johnson, the heir to the Johnson & Johnson fortune and the owner of the New York Jets NFL team. Johnson was a major Trump donor and was appointed by the president.

“There’s a higher level of mistrust from political ambassadors of career [foreign services officers] than I’ve ever seen in my life,” Lukens told GQ. “Many of Trump’s political ambassadors have an unfounded belief that government bureaucrats are overwhelmingly Democrats and liberals and working against Trump’s agenda, and that’s just not the case.”

The State Department has yet to comment Lukens’s claim that he was fired for talking positively about Obama. Lukens tweeted briefly about the article in the hours after it published, thanking a Harvard professor who backed him for her “support and kind words.”

Trump has a long history of going after Obama: the billionaire led the charge on the racist, debunked birther conspiracy and his administration has actively worked to undermine Obama’s signature achievements. The Trump administration has also let a severely understaffed State Department flounder. GQ cited the Lukens incident as an example of experienced diplomats being pushed out in favor of political appointees who are often diplomatic novices.

“It’s a hollowing out of the foreign service,” Nicholas Burns, a retired career foreign service officer, told the magazine. “You can’t replace those mid-level people easily at the numbers at which they’re losing them. That will take a generation to rebuild.”