diff --git a/src/newgrf_engine.h b/src/newgrf_engine.h
--- a/src/newgrf_engine.h
+++ b/src/newgrf_engine.h
@@ -30,8 +30,8 @@ void SetEngineGRF(EngineID engine, const
 const struct GRFFile *GetEngineGRF(EngineID engine);
 uint32 GetEngineGRFID(EngineID engine);
 
-uint16 GetVehicleCallback(uint16 callback, uint32 param1, uint32 param2, EngineID engine, const Vehicle *v);
-uint16 GetVehicleCallbackParent(uint16 callback, uint32 param1, uint32 param2, EngineID engine, const Vehicle *v, const Vehicle *parent);
+uint16 GetVehicleCallback(CallbackID callback, uint32 param1, uint32 param2, EngineID engine, const Vehicle *v);
+uint16 GetVehicleCallbackParent(CallbackID callback, uint32 param1, uint32 param2, EngineID engine, const Vehicle *v, const Vehicle *parent);
 bool UsesWagonOverride(const Vehicle *v);
 #define GetCustomVehicleSprite(v, direction) GetCustomEngineSprite(v->engine_type, v, direction)
 #define GetCustomVehicleIcon(et, direction) GetCustomEngineSprite(et, NULL, direction)