diff --git a/cura/Settings/ContainerManager.py b/cura/Settings/ContainerManager.py
index cb3ae88914..e3a0d22299 100644
--- a/cura/Settings/ContainerManager.py
+++ b/cura/Settings/ContainerManager.py
@@ -349,6 +349,9 @@ class ContainerManager(QObject):
         except NotImplementedError:
             return { "status": "error", "message": "Unable to serialize container"}
 
+        if contents is None:
+            return {"status": "error", "message": "Serialization returned None. Unable to write to file"}
+
         with UM.SaveFile(file_url, "w") as f:
             f.write(contents)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py b/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
index cab1c00852..6510d34cb1 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
@@ -91,12 +91,9 @@ class MachineInstance:
 
         if has_machine_qualities: #This machine now has machine-quality profiles.
             active_material += "_" + variant_materials #That means that the profile was split into multiple.
-            current_settings = "" #The profile didn't know the definition ID when it was upgraded, so it will have been invalid. Sorry, your current settings are lost now.
-        else:
-            current_settings = self._name + "_current_settings"
 
         containers = [
-            current_settings,
+            "", #The current profile doesn't know the definition ID when it was upgraded, only the instance ID, so it will be invalid. Sorry, your current settings are lost now.
             active_quality_changes,
             active_quality,
             active_material,
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py b/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
index 6c940b97cf..ff404c0398 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
@@ -80,7 +80,7 @@ class Profile:
         import VersionUpgrade21to22 # Import here to prevent circular dependencies.
 
         if self._name == "Current settings":
-            self._filename += "_current_settings" #This resolves a duplicate ID arising from how Cura 2.1 stores its current settings.
+            return None #Can't upgrade these, because the new current profile needs to specify the definition ID and the old file only had the machine instance, not the definition.
 
         config = configparser.ConfigParser(interpolation = None)
 
diff --git a/plugins/XmlMaterialProfile/XmlMaterialProfile.py b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
index 58e7a89cad..bf3f34b667 100644
--- a/plugins/XmlMaterialProfile/XmlMaterialProfile.py
+++ b/plugins/XmlMaterialProfile/XmlMaterialProfile.py
@@ -85,9 +85,6 @@ class XmlMaterialProfile(UM.Settings.InstanceContainer):
     # base file: global settings + supported machines
     # machine / variant combination: only changes for itself.
     def serialize(self):
-        if self._read_only:
-            return
-
         registry = UM.Settings.ContainerRegistry.getInstance()
 
         base_file = self.getMetaDataEntry("base_file", "")