Sarah Huckabee Sanders flat-out lied about the addition of a citizenship question to the census. And even Fox News' Steve Doocy knew it.

Sarah Huckabee Sanders told a lie so egregious that even “Fox & Friends” host Steve Doocy couldn’t help but set the record straight, if unintentionally.

The Trump administration is being sued over its decision to add a question about citizenship to the 2020 census. But when reporters pressed Sanders about it during a briefing, she simply lied.

Sanders told reporters that the citizenship question has “been included in every census since 1965 with the exception of 2010.” She repeated the lie three separate times.

But on Wednesday morning’s edition of “Fox & Friends,” Doocy gave away the game.

“Apparently, they stopped doing it about 70 years ago,” he said. “I was reading about it in the Wall Street Journal today. It’s interesting. They stopped asking it because there were so few non-citizens in the United States of America, and they probably wanted to make room for more questions.”

“They have been asking that question every year on a survey that goes out, but not to as many houses,” Doocy added.

Doocy is surprisingly correct, for the most part. According to Mother Jones, the question was last included on the census in 1950. It has been included on the American Community Survey since then. But that’s not the official census, and it doesn’t determine representation.

That survey only goes to about 15 percent of homes. So Doocy’s comment that it’s sent “not to as many houses” is a gross understatement.

The article that Doocy cites notes that the question was removed to make room for others, according to one historian.

This marks two days in a row that Fox News personalities delivered bad news about the census. On Tuesday, Judge Andrew Napolitano crushed Brian Kilmeade’s spirits with the news that the U.S. Constitution isn’t on Trump’s side in the census dispute.

Sanders is already well known for lying on Trump’s behalf. But it’s rather uncommon for her lies to be called out by Fox News, rather than the reporters in the briefing room.