diff --git a/cura/Machines/MaterialNode.py b/cura/Machines/MaterialNode.py
index 91b6601dc8..7d71b24939 100644
--- a/cura/Machines/MaterialNode.py
+++ b/cura/Machines/MaterialNode.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2019 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-from typing import Any, TYPE_CHECKING
+from typing import Any, Optional, TYPE_CHECKING
 
 from UM.Logger import Logger
 from UM.Settings.ContainerRegistry import ContainerRegistry
@@ -29,7 +29,10 @@ class MaterialNode(ContainerNode):
         self.base_file = my_metadata["base_file"]
         self.material_type = my_metadata["material"]
         self.guid = my_metadata["GUID"]
-        self.diameter = my_metadata["properties"]["diameter"]
+        # MaterialNode can represent an empty_material container, which has no diameter.
+        self.diameter = None  # type: Optional[str]
+        if "properties" in my_metadata:
+            self.diameter = my_metadata["properties"]["diameter"]
         self._loadAll()
         container_registry.containerRemoved.connect(self._onRemoved)
         container_registry.containerMetaDataChanged.connect(self._onMetadataChanged)
@@ -130,7 +133,8 @@ class MaterialNode(ContainerNode):
         self.material_type = new_metadata["material"]
         old_guid = self.guid
         self.guid = new_metadata["GUID"]
-        self.diameter = new_metadata["properties"]["diameter"]
+        if "properties" in new_metadata:
+            self.diameter = new_metadata["properties"]["diameter"]
         if self.base_file != old_base_file or self.material_type != old_material_type or self.guid != old_guid:  # List of quality profiles could've changed.
             self.qualities = {}
             self._loadAll()  # Re-load the quality profiles for this node.