diff --git a/cura/Settings/MachineManager.py b/cura/Settings/MachineManager.py
index 5c6769bc7d..124cff73d8 100755
--- a/cura/Settings/MachineManager.py
+++ b/cura/Settings/MachineManager.py
@@ -1236,7 +1236,7 @@ class MachineManager(QObject):
     ##  Given a printer definition name, select the right machine instance. In case it doesn't exist, create a new
     #   instance with the same network key.
     @pyqtSlot(str)
-    def switchPrinterType(self, machine_name: str):
+    def switchPrinterType(self, machine_name: str) -> None:
         # Don't switch if the user tries to change to the same type of printer
         if self.activeMachineDefinitionName == machine_name:
             return
@@ -1247,6 +1247,8 @@ class MachineManager(QObject):
         # If there is no machine, then create a new one and set it to the non-hidden instance
         if not new_machine:
             new_machine = CuraStackBuilder.createMachine(machine_definition_id + "_sync", machine_definition_id)
+            if not new_machine:
+                return
             new_machine.addMetaDataEntry("um_network_key", self.activeMachineNetworkKey)
             new_machine.addMetaDataEntry("connect_group_name", self.activeMachineNetworkGroupName)
             new_machine.addMetaDataEntry("hidden", False)
diff --git a/plugins/3MFReader/ThreeMFWorkspaceReader.py b/plugins/3MFReader/ThreeMFWorkspaceReader.py
index 76afb6b47e..9375e5d6ee 100755
--- a/plugins/3MFReader/ThreeMFWorkspaceReader.py
+++ b/plugins/3MFReader/ThreeMFWorkspaceReader.py
@@ -606,9 +606,10 @@ class ThreeMFWorkspaceReader(WorkspaceReader):
             machine_name = self._container_registry.uniqueName(self._machine_info.name)
 
             global_stack = CuraStackBuilder.createMachine(machine_name, self._machine_info.definition_id)
-            extruder_stack_dict = global_stack.extruders
+            if global_stack: #Only switch if creating the machine was successful.
+                extruder_stack_dict = global_stack.extruders
 
-            self._container_registry.addContainer(global_stack)
+                self._container_registry.addContainer(global_stack)
         else:
             # Find the machine
             global_stack = self._container_registry.findContainerStacks(name = self._machine_info.name, type = "machine")[0]