diff --git a/src/object_cmd.cpp b/src/object_cmd.cpp
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@@ -486,7 +486,7 @@ static void DrawTile_Object(TileInfo *ti
 	DrawBridgeMiddle(ti);
 }
 
-static int GetSlopePixelZ_Object(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Object(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	if (IsObjectType(tile, OBJECT_OWNED_LAND)) {
 		int z;