While attempting to attack an amendment to the “Gang of Eight” immigration bill that would require a fence be built along Mexico’s border with the U.S. before legalization, Sen. Mary Landrieu (D-LA) made a significant geographical gaffe.

Landrieu, who represents Louisiana in the U.S. Senate, was trying to undermine the amendment Sen. John Thune (R-SD) offered. In doing so, she tried to argue Sen. John McCain (R-AZ) was more qualified to talk about border issues than Thune because McCain represents Arizona.

“A smart fence, which is what Senator McCain and I want to build–since he’s from Arizona, I think he knows more about this than the Senator from South Dakota who only has a border with Canada and that is quite different,” Landrieu said.

South Dakota does not share a border with Canada. It does, however, share borders with North Dakota, Wyoming, Montana, Minnesota, Nebraska and Iowa.

Landrieu went on to argue that the 700-mile border double-fence that Congress passed into law a few years ago is a “dumb fence.” She said she would be “voting against” Thune’s amendment requiring the implementation of current law because of she thinks the fence is “dumb.”

“So I would be voting against Senator Thune’s amendment because I’m not going to waste taxpayer money on a dumb fence, and that’s what his amendment would be,” Landrieu said. “We need to build a smart fence and a fence is not just a physical structure which could be built out of a variety of different materials with or without barbed wire on the top.”

Thune came back to the floor after Landrieu’s comments to note that the Louisiana Democrat actually voted for the “dumb fence” a few years ago. “I would say in response to my colleague from Louisiana that we all voted for this,” Thune said.

“I mean this is not–she described it as a dumb fence. I guess I didn’t realize it was a dumb fence. I thought it was a commitment we made to the American people to get serious about securing the border,” Thune explained. “There are other ways–I would certainly concede–other ways in which we can combine manpower, technology, infrastructure along the border to make it more secure.”

Afterward, Landrieu came back to the floor to respond to Thune: “You are correct, I voted for the dumb fence once, I’m not going to do it again because I learned my mistake.”