--- a/src/road_internal.h	Mon Apr 14 20:32:36 2008 +0000
+++ b/src/road_internal.h	Tue Apr 15 00:47:19 2008 +0000
@@ -31,6 +31,6 @@
  * @param ti   information about the tile (position, slope)
  * @param tram the roadbits to draw the catenary for
  */
-void DrawTramCatenary(TileInfo *ti, RoadBits tram);
+void DrawTramCatenary(const TileInfo *ti, RoadBits tram);
 
 #endif /* ROAD_INTERNAL_H */