diff --git a/src/script/api/script_tile.cpp b/src/script/api/script_tile.cpp
index b14bea649e..c84e8411a6 100644
--- a/src/script/api/script_tile.cpp
+++ b/src/script/api/script_tile.cpp
@@ -43,10 +43,11 @@
 
 /* static */ bool ScriptTile::IsBuildableRectangle(TileIndex tile, uint width, uint height)
 {
-	uint tx, ty;
+	/* Check whether we can extract valid X and Y */
+	if (!::IsValidTile(tile)) return false;
 
-	tx = ScriptMap::GetTileX(tile);
-	ty = ScriptMap::GetTileY(tile);
+	uint tx = ScriptMap::GetTileX(tile);
+	uint ty = ScriptMap::GetTileY(tile);
 
 	for (uint x = tx; x < width + tx; x++) {
 		for (uint y = ty; y < height + ty; y++) {