diff --git a/plugins/3MFWriter/ThreeMFWorkspaceWriter.py b/plugins/3MFWriter/ThreeMFWorkspaceWriter.py
index 95aac49f55..f805936ab5 100644
--- a/plugins/3MFWriter/ThreeMFWorkspaceWriter.py
+++ b/plugins/3MFWriter/ThreeMFWorkspaceWriter.py
@@ -90,6 +90,6 @@ class ThreeMFWorkspaceWriter(WorkspaceWriter):
 
         # Do not include the network authentication keys
         ignore_keys = ["network_authentication_id", "network_authentication_key"]
-        serialized_data = container.serialize(ignore_metadata_keys = ignore_keys)
+        serialized_data = container.serialize(ignored_metadata_keys = ignore_keys)
 
         archive.writestr(file_in_archive, serialized_data)
diff --git a/plugins/XmlMaterialProfile/XmlMaterialProfile.py b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
index da04ed7dc9..f920a6bd49 100644
--- a/plugins/XmlMaterialProfile/XmlMaterialProfile.py
+++ b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
@@ -3,7 +3,7 @@
 
 import copy
 import io
-from typing import Optional
+from typing import List, Optional
 import xml.etree.ElementTree as ET
 
 from UM.Resources import Resources
@@ -109,7 +109,7 @@ class XmlMaterialProfile(InstanceContainer):
     ##  Overridden from InstanceContainer
     # base file: common settings + supported machines
     # machine / variant combination: only changes for itself.
-    def serialize(self, ignore_metadata_keys=[]):
+    def serialize(self, ignored_metadata_keys: Optional[List] = None):
         registry = ContainerRegistry.getInstance()
 
         base_file = self.getMetaDataEntry("base_file", "")
@@ -130,9 +130,11 @@ class XmlMaterialProfile(InstanceContainer):
 
         metadata = copy.deepcopy(self.getMetaData())
         # setting_version is derived from the "version" tag in the schema, so don't serialize it into a file
-        ignore_metadata_keys = ignore_metadata_keys + ["setting_version"]
+        if ignored_metadata_keys is None:
+            ignored_metadata_keys = []
+        ignored_metadata_keys = ignored_metadata_keys + ["setting_version"]
         # remove the keys that we want to ignore in the metadata
-        for key in ignore_metadata_keys:
+        for key in ignored_metadata_keys:
             if key in metadata:
                 del metadata[key]
         properties = metadata.pop("properties", {})