Lt. Col. Alexander Vindman snapped at ranking member Rep. Devin Nunes after he referred to him as “Mr. Vindman.”

During his public impeachment testimony on Tuesday, Vindman was taking a line of questioning from Nunes when the California Republican referred to him as “Mr. Vindman” rather than his official military title.

“Mr. Vindman, you testified in your deposition that you did not know the whistleblower,” Nunes said.

Vindman replied, “Ranking member, it’s Lt. Col. Vindman, please.”

Nunes corrected Vindman’s title and repeated the question. Vindman claimed that he was advised by his attorney not to answer questions related to the whistleblower.

Vindman, 44, was the top Ukraine specialist on the National Security Council during President Trump’s phone call with Ukrainian President Volodymyr Zelensky.