diff --git a/openttd.h b/openttd.h
--- a/openttd.h
+++ b/openttd.h
@@ -295,7 +295,6 @@ typedef struct {
 	byte width_1, width_2;
 } ViewportSign;
 
-typedef int32 CommandProc(int x, int y, uint32 flags, uint32 p1, uint32 p2);
 
 typedef void DrawTileProc(TileInfo *ti);
 typedef uint GetSlopeZProc(const TileInfo* ti);