An innocuous tweet showing the Clinton campaign setting up for a New Hampshire event caused a Twitter storm among veterans earlier this week. If you’ve ever read up on the U.S. Flag Code, you can probably see why:

On the night of the New Hampshire primary, Clinton’s campaign decorated its venue with many American flags. This tweet, however, suggests that between unpacking the flags and mounting them on the wall, they might have been left crumpled on the floor.

Veterans teamed up with the Twitterati to piece together the context of the photo and determine whether or not the U.S. Flag Code was followed.

According to Title 4, Article 8 of the code, “The flag should never touch anything beneath it, such as the ground, the floor, water or merchandise.” While the offending photo makes it unclear whether the flag is truly on the floor or resting on bleachers, the manner in which it is crumpled was enough to make veterans demand a response from the candidate.

Following the backlash, the Clinton campaign issued a public apology.

“Hillary Clinton and her team have the utmost respect for the flag and for those who serve,” a Clinton staff member said. “A contractor clearly made a mistake in leaving the flag on a stage. We have made clear to our team this is unacceptable.”