--- a/newgrf_engine.c	Sat Apr 29 14:31:16 2006 +0000
+++ b/newgrf_engine.c	Sun Apr 30 18:19:37 2006 +0000
@@ -18,7 +18,7 @@
 typedef struct WagonOverride {
 	byte *train_id;
 	int trains;
-	SpriteGroup *group;
+	const SpriteGroup *group;
 } WagonOverride;
 
 typedef struct WagonOverrides {
@@ -28,8 +28,7 @@
 
 static WagonOverrides _engine_wagon_overrides[TOTAL_NUM_ENGINES];
 
-void SetWagonOverrideSprites(EngineID engine, SpriteGroup *group, byte *train_id,
-	int trains)
+void SetWagonOverrideSprites(EngineID engine, const SpriteGroup *group, byte *train_id, int trains)
 {
 	WagonOverrides *wos;
 	WagonOverride *wo;
@@ -98,10 +97,10 @@
 // (It isn't and shouldn't be like this in the GRF files since new cargo types
 // may appear in future - however it's more convenient to store it like this in
 // memory. --pasky)
-static SpriteGroup *engine_custom_sprites[TOTAL_NUM_ENGINES][NUM_GLOBAL_CID];
+static const SpriteGroup *engine_custom_sprites[TOTAL_NUM_ENGINES][NUM_GLOBAL_CID];
 static uint32 _engine_grf[TOTAL_NUM_ENGINES];
 
-void SetCustomEngineSprites(EngineID engine, byte cargo, SpriteGroup *group)
+void SetCustomEngineSprites(EngineID engine, byte cargo, const SpriteGroup *group)
 {
 	assert(engine < TOTAL_NUM_ENGINES);
 	if (engine_custom_sprites[engine][cargo] != NULL) {

--- a/newgrf_engine.h	Sat Apr 29 14:31:16 2006 +0000
+++ b/newgrf_engine.h	Sun Apr 30 18:19:37 2006 +0000
@@ -14,9 +14,8 @@
 VARDEF const CargoID _local_cargo_id_ctype[NUM_GLOBAL_CID];
 VARDEF const uint32 cargo_classes[16];
 
-void SetWagonOverrideSprites(EngineID engine, struct SpriteGroup *group, byte *train_id, int trains);
-void SetCustomEngineSprites(EngineID engine, byte cargo, struct SpriteGroup *group);
-// loaded is in percents, overriding_engine 0xffff is none
+void SetWagonOverrideSprites(EngineID engine, const struct SpriteGroup *group, byte *train_id, int trains);
+void SetCustomEngineSprites(EngineID engine, byte cargo, const struct SpriteGroup *group);
 SpriteID GetCustomEngineSprite(EngineID engine, const Vehicle* v, Direction direction);
 
 void SetEngineGRF(EngineID engine, uint32 grfid);