Army Lt. Col. Alexander Vindman made sure to take the time to correct a Congressman on Tuesday while testifying before Congress, requesting that he be addressed by his officer rank and not “Mr.”

“Mr. Vindman, you testified in your deposition that you did not know the whistleblower, correct?” Rep. Devin Nunes, the Ranking Member of the House Intelligence Committee asked.

“Ranking Member, it's Lt. Col. Vindman, please,” Vindman responded.

Rep. Chris Stewart (R-Utah) later asked Vindman if he typically requires civilians to address him by his rank, to which Vindman said because he's in uniform, he “thought it was appropriate to stick to that.”

“The Ranking Member meant no disrespect to you,” Stewart said.

“I believe that,” Vindman responded.

Vindman is testifying before Congress as lawmakers move forward with an impeachment inquiry into President Donald Trump, which centers on a July 25 phone call with Ukrainian president Volodymyr Zelensky. Vindman, a Ukraine expert on the National Security Council, was listening in on the call in his official capacity.

Vindman, a career Army official, has been indirectly called a “Never Trumper” by the president; he told lawmakers this morning that he would call himself a “never partisan.” He also told the committee that it's been “an honor” to dedicate his life to the country he and his family fled to from the then-Soviet Union.

“The uniform I wear today is that of the United States Army,” Vindman said in his opening statement.

“I am humbled to come before you today as one of many who serve in the most distinguished and able military in the world. The Army is the only profession I have ever known. As a young man I decided that I wanted to spend my life serving the nation that gave my family refuge from authoritarian oppression, and for the last twenty years it has been an honor to represent and protect this great country.”