--- a/src/vehicle.cpp	Wed May 14 15:29:48 2008 +0000
+++ b/src/vehicle.cpp	Wed May 14 15:34:04 2008 +0000
@@ -1552,7 +1552,7 @@
  * @param color The string to show depending on if we are unloading or loading
  * @return A percentage of how full the Vehicle is.
  */
-uint8 CalcPercentVehicleFilled(Vehicle *v, StringID *color)
+uint8 CalcPercentVehicleFilled(const Vehicle *v, StringID *color)
 {
 	int count = 0;
 	int max = 0;

--- a/src/vehicle_func.h	Wed May 14 15:29:48 2008 +0000
+++ b/src/vehicle_func.h	Wed May 14 15:34:04 2008 +0000
@@ -31,7 +31,7 @@
 void *VehicleFromPosXY(int x, int y, void *data, VehicleFromPosProc *proc);
 void CallVehicleTicks();
 Vehicle *FindVehicleOnTileZ(TileIndex tile, byte z);
-uint8 CalcPercentVehicleFilled(Vehicle *v, StringID *color);
+uint8 CalcPercentVehicleFilled(const Vehicle *v, StringID *color);
 
 void InitializeTrains();
 byte VehicleRandomBits();