For the most part, the 390-mile border between France and Belgium has remained unchanged since 1820, when it was made official by the Treaty of Kortrijk. The line is marked by a series of tombstone-like blocks engraved with 1819 (the year they were installed) and weighing at least a few hundred pounds each. In other words, they’re not the type of stones you could accidentally kick out of place—which is good, since relocating one would alter the border and put you at risk for criminal charges.

For one Belgian farmer, that situation isn’t purely hypothetical. According to The New York Times, the unnamed culprit recently shifted a stone a little over 7 feet into northern France, expanding his own property ... along with the border of his entire country. We don’t yet know whether the farmer understood what the stone was, let alone the possible consequences of displacing it. But it’s been reported that he was just trying to make it easier to drive his tractor around the plot. The fence along the edge of his land had also been shifted onto French territory.

The transgression was discovered not by drones or other geo-tracking technology, but by some French history enthusiasts who used an old map to compare the stones’ current locations to their original spots. As soon as they saw this particular stone in April, they thought it seemed off.

“All the markers are typically placed in a very precise manner, but this one was raised up on higher ground. It just looked strange,” Jean-Pierre Chopin, a member of the group, told The New York Times.

It’s now up to the head official on each side of the border—David Lavaux of Erquelinnes, Belgium, and Aurélie Welonek of Bousignies-sur-Roc, France—to sort out the issue. As long as the farmer agrees to replace the marker, they don’t plan on taking further action. “We have no interest in expanding the town, or the country,” Lavaux joked to France Bleu.

[h/t The New York Times]