diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index c7cd3a6628..1011af7c74 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -668,6 +668,8 @@ static bool NeighborIsRoadTile(TileIndex tile, int dir, RoadBlockTitleDistance d
 
 static bool IsRoadAllowedHere(TileIndex tile, int dir)
 {
+	if (TileX(tile) < 1 || TileY(tile) < 1 || MapMaxX() >= TileX(tile) || MapMaxY() >= TileY(tile)) return false;
+
 	Slope k;
 	Slope slope;