Caution ahead…Hillary for prison.

That was the warning message that had Dallas drivers doing a double take on Saturday.

Someone “hacked” a construction warning sign in I-30 to read “Hillary for prison,” Fox 4 reports.

The prankster also included, “Free Barrett Brown,” a reference to a Dallas writer with ties to the “hacktivist” collective Anonymous, according to The Dallas Morning News.

“Tampering with a warning sign is a misdemeanor crime that is punishable by a fine of up to $1,000 and up to two years in jail,” Fox 4 notes.

Last December, a California construction sign was hacked to change the message to advocate for Donald Trump.

Nikki Miles Worden was driving in Corona, California Saturday when the road construction sign caught her eye.

“Inland Empire supports Donald Trump. Merry Xmas. Vote Donald Trump,” it read.

“Had to turn around and record this,” Worden wrote on Facebook.

The sign was posted on the northbound 15 freeway.

A Caltrans spokesperson tells ABC 7 someone apparently “reprogrammed” the sign. It was changed back soon after.