diff --git a/src/newgrf.h b/src/newgrf.h
index 9058aea32a..a02b0021ff 100644
--- a/src/newgrf.h
+++ b/src/newgrf.h
@@ -126,7 +126,7 @@ struct GRFFile : ZeroedMemoryAllocator {
 	uint8 cargo_map[NUM_CARGO];                     ///< Inverse cargo translation table (CargoID -> local ID)
 
 	SmallVector<RailTypeLabel, 4> railtype_list;    ///< Railtype translation table
-	RailType railtype_map[RAILTYPE_END];
+	RailTypeByte railtype_map[RAILTYPE_END];
 
 	CanalProperties canal_local_properties[CF_END]; ///< Canal properties as set by this NewGRF