diff --git a/src/pathfinder/water_regions.cpp b/src/pathfinder/water_regions.cpp
index 6ef8d2c998..9cfb9c7729 100644
--- a/src/pathfinder/water_regions.cpp
+++ b/src/pathfinder/water_regions.cpp
@@ -324,7 +324,8 @@ void InvalidateWaterRegion(TileIndex tile)
 	 * traversability. This means that if we invalidate any region edge tiles we might also change the traversability
 	 * of the adjacent region. This code ensures the adjacent regions also get invalidated in such a case. */
 	for (DiagDirection side = DIAGDIR_BEGIN; side < DIAGDIR_END; side++) {
-		const TileIndex adjacent_tile = TileAddByDiagDir(tile, side);
+		const TileIndex adjacent_tile = AddTileIndexDiffCWrap(tile, TileIndexDiffCByDiagDir(side));
+		if (adjacent_tile == INVALID_TILE) continue;
 		if (GetWaterRegionIndex(adjacent_tile) != GetWaterRegionIndex(tile)) invalidate_region(adjacent_tile);
 	}
 }