diff --git a/cura/Machines/MachineNode.py b/cura/Machines/MachineNode.py
index 1a2369ecd2..114be73338 100644
--- a/cura/Machines/MachineNode.py
+++ b/cura/Machines/MachineNode.py
@@ -21,6 +21,9 @@ class MachineNode(ContainerNode):
         self.variants = {}  # type: Dict[str, VariantNode] # mapping variant names to their nodes.
         container_registry = ContainerRegistry.getInstance()
         my_metadata = container_registry.findContainersMetadata(id = container_id)[0]
+        # Some of the metadata is cached upon construction here.
+        # ONLY DO THAT FOR METADATA THAT DOESN'T CHANGE DURING RUNTIME!
+        # Otherwise you need to keep it up-to-date during runtime.
         self.has_machine_materials = parseBool(my_metadata.get("has_machine_materials", "false"))
         self.has_machine_quality = parseBool(my_metadata.get("has_machine_quality", "false"))
         self.quality_definition = my_metadata.get("quality_definition", container_id)