diff --git a/cura/Machines/ContainerNode.py b/cura/Machines/ContainerNode.py
index 14739eedd8..944579e354 100644
--- a/cura/Machines/ContainerNode.py
+++ b/cura/Machines/ContainerNode.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-from typing import Optional, Any, Dict
+from typing import Optional, Any, Dict, Union, TYPE_CHECKING
 
 from collections import OrderedDict
 
@@ -9,6 +9,9 @@ from UM.ConfigurationErrorMessage import ConfigurationErrorMessage
 from UM.Logger import Logger
 from UM.Settings.InstanceContainer import InstanceContainer
 
+if TYPE_CHECKING:
+    from cura.Machines.QualityGroup import QualityGroup
+
 
 ##
 # A metadata / container combination. Use getContainer() to get the container corresponding to the metadata.
@@ -26,7 +29,7 @@ class ContainerNode:
     def __init__(self, metadata: Optional[Dict[str, Any]] = None) -> None:
         self.metadata = metadata
         self.container = None
-        self.children_map = OrderedDict() #type: OrderedDict[str, ContainerNode]
+        self.children_map = OrderedDict() #type: OrderedDict[str, Union[QualityGroup, ContainerNode]]
 
     ##  Get an entry value from the metadata
     def getMetaDataEntry(self, entry: str, default: Any = None) -> Any:
diff --git a/cura/Machines/MaterialGroup.py b/cura/Machines/MaterialGroup.py
index eea9e41d62..b57e0e1808 100644
--- a/cura/Machines/MaterialGroup.py
+++ b/cura/Machines/MaterialGroup.py
@@ -21,7 +21,7 @@ class MaterialGroup:
     def __init__(self, name: str, root_material_node: MaterialNode) -> None:
         self.name = name
         self.is_read_only = False
-        self.root_material_node = root_material_node
+        self.root_material_node = root_material_node # type: MaterialNode
         self.derived_material_node_list = [] #type: List[MaterialNode]
 
     def __str__(self) -> str:
diff --git a/cura/Machines/QualityNode.py b/cura/Machines/QualityNode.py
index 922227b022..f384ee7825 100644
--- a/cura/Machines/QualityNode.py
+++ b/cura/Machines/QualityNode.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-from typing import Optional, Dict
+from typing import Optional, Dict, cast
 
 from .ContainerNode import ContainerNode
 from .QualityChangesGroup import QualityChangesGroup
@@ -32,4 +32,4 @@ class QualityNode(ContainerNode):
         if name not in quality_type_node.children_map:
             quality_type_node.children_map[name] = QualityChangesGroup(name, quality_type)
         quality_changes_group = quality_type_node.children_map[name]
-        quality_changes_group.addNode(QualityNode(metadata))
+        cast(QualityChangesGroup, quality_changes_group).addNode(QualityNode(metadata))