diff --git a/train_cmd.c b/train_cmd.c
--- a/train_cmd.c
+++ b/train_cmd.c
@@ -700,6 +700,7 @@ static void AddRearEngineToMultiheadedTr
  * @param tile tile of the depot where rail-vehicle is built
  * @param p1 engine type id
  * @param p2 bit 0 prevents any free cars from being added to the train
+ *           bit 1 when set, the train will get number 0, otherwise it will get a free number
  */
 int32 CmdBuildRailVehicle(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
 {
@@ -743,10 +744,14 @@ int32 CmdBuildRailVehicle(TileIndex tile
 
 		v = vl[0];
 
-		unit_num = GetFreeUnitNumber(VEH_Train);
-		if (unit_num > _patches.max_trains)
-			return_cmd_error(STR_00E1_TOO_MANY_VEHICLES_IN_GAME);
-
+		if (HASBIT(p2, 1)) {
+			// no number is needed, so we assign 0. The engine is likely intended for a train with more than one engine
+			unit_num = 0;
+		} else {
+			unit_num = GetFreeUnitNumber(VEH_Train);
+			if (unit_num > _patches.max_trains)
+				return_cmd_error(STR_00E1_TOO_MANY_VEHICLES_IN_GAME);
+		}
 		if (flags & DC_EXEC) {
 			DiagDirection dir = GetRailDepotDirection(tile);
 			int x = TileX(tile) * TILE_SIZE + _vehicle_initial_x_fract[dir];