diff --git a/city_model_structure/city.py b/city_model_structure/city.py
index b4c8cbea..780d8e35 100644
--- a/city_model_structure/city.py
+++ b/city_model_structure/city.py
@@ -17,6 +17,8 @@ from city_model_structure.building import Building
 from city_model_structure.city_object import CityObject
 from city_model_structure.city_objects_cluster import CityObjectsCluster
 from city_model_structure.buildings_cluster import BuildingsCluster
+from city_model_structure.fuel import Fuel
+from city_model_structure.machine import Machine
 from city_model_structure.parts_consisting_building import PartsConsistingBuilding
 from city_model_structure.subway_entrance import SubwayEntrance
 from helpers.geometry_helper import GeometryHelper