diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -261,7 +261,7 @@ CommandCost CmdSetRoadDriveSide(TileInde
 		_opt_ptr->road_side = p1;
 		InvalidateWindow(WC_GAME_OPTIONS,0);
 	}
-	return 0;
+	return CommandCost();
 }
 
 static const Widget _game_options_widgets[] = {