diff -r f37aaf33593b src/order_cmd.cpp
--- a/src/order_cmd.cpp	Sun Jan 04 14:55:04 2009 +0100
+++ b/src/order_cmd.cpp	Sun Jan 04 16:09:29 2009 +0100
@@ -643,6 +643,10 @@
 	}
 
 	if (sel_ord > v->GetNumOrders()) return CMD_ERROR;
+
+	/** v->orders.list->num_orders == INVALID_VEH_ORDER_ID would mean that the OrderList is invalid
+	 * therefore we cannot allow the number of orders to become bigger than INVALID_VEH_ORDER_ID - 1 */
+	if (v->GetNumOrders() >= INVALID_VEH_ORDER_ID - 1) return_cmd_error(STR_8832_TOO_MANY_ORDERS);
 
 	if (!Order::CanAllocateItem()) return_cmd_error(STR_8831_NO_MORE_SPACE_FOR_ORDERS);
 	if (v->orders.list == NULL && !OrderList::CanAllocateItem()) return_cmd_error(STR_8831_NO_MORE_SPACE_FOR_ORDERS);