A typo on a billboard for the University of South Dakota is small but important.

CBS News in Minnesota reported.

Oops! University Of South Dakota Billboard Contains Grammar Error

A University of South Dakota billboard with a grammatical error reflects badly on the university and will be replaced, the school’s spokeswoman says.

The billboard along Interstate 90 west of Sioux Falls quotes Forbes magazine saying USD is the “Best in the Dakota’s,” but the apostrophe makes the word “Dakotas” possessive rather than plural.

USD spokeswoman Tena Haraldson told the Argus Leader newspaperand KELO-TV that the mistake was human error — the wrong version of a design got sent to the billboard company.

“We all recognized here when we looked at it that the apostrophe was misplaced,” she said. “It was just an oversight that that’s the one that was grabbed and put up. It happens.”

USD alum Lyndsey Kastein, a strategist at a Sioux Falls marketing firm, told the Argus Leader that she’s embarrassed by the sign.

“I didn’t even learn proper grammar in college — I learned that in elementary school,” she said. “So it’s just sort of inexcusable.”