Indie games always dream of having a big impact, but not quite the one Prison Architect managed to achieve. The game makers were made aware their game was in violation of the Geneva Conventions thanks to just five very particular pixels, according to a report from PC Gamer.

The issue arose thanks to the appearance of a five-pixel wide red cross on the hood of the ambulances and backpacks of paramedics in the game. Game producer Mark Morris and designer Chris Delay of Introversion Software were unaware that symbol happened to be internationally protected until a letter from the British Red Cross arrived at their studio.

"My immediate reason for writing is that it has been brought to our attention that in your game ‘Prison Architect’ a red cross emblem is displayed on vehicles," the letter read. "Those responsible may be unaware that use of the red cross emblem is restricted under the Geneva Conventions for the Protection of War Victims of 12 August 1949, and that unauthorised use of this sign in the United Kingdom is an offence under the Geneva Conventions Act 1957."

Despite initially thinking it was some sort of prank, the team found out the protections on the easily identifiable red cross icon is no joke.

The red cross is a protected emblem of the International Committee of the Red Cross (ICRC), an organization that started in 1863. The ICRC helped establish the Geneva Conventions —rules that apply in times of armed conflict and are intended to protect people who are not taking part in hostilities.

Those same rules also made the red cross a universally recognized symbol of protection during armed conflicts, used to safeguard the wounded and sick and those who help them.

Misuse of the iconography is prohibited to prevent armed forces from misrepresenting themselves in order to gain an advantage in battle. Using the symbol without permission—like Colombian military members did in order to rescue political prisoners held by rebel forces—is considered to be a war crime.

While its presence in Prison Architect isn’t likely to cause any sort of misunderstanding, the ICRC takes its symbol seriously.

"If the red cross emblem or similar signs are used for other purposes, no matter how beneficial or inconsequential they may seem, the special significance of the emblem will be diminished," the email said. "The red cross emblem or similar designs are not general signs of ambulances, health care, first aid, the nursing or medical profession, or similar matters.”

According to the ICRC’s email, the red cross is also not meant to be used for commercial purposes, such as for advertising campaigns or on products.

Prison Architect isn’t the first game to be put on notice by the ICRC. In 2006, the Canadian Red Cross sent a letter to several game developers in hopes of convincing them to stop using the icon in their games.

Upon receiving the notice from the Red Cross—and spooked by the specter that they may be in violation of international laws—the team behind Prison Architect quickly complied with the request. The cross that appears on paramedics in the game is now green instead of red.