diff --git a/cura/Settings/ExtruderManager.py b/cura/Settings/ExtruderManager.py
index 8fa0172305..4f1a2c5a4e 100755
--- a/cura/Settings/ExtruderManager.py
+++ b/cura/Settings/ExtruderManager.py
@@ -341,7 +341,7 @@ class ExtruderManager(QObject):
                 extruder_train.setNextStack(global_stack)
                 extruders_changed = True
 
-            self._fixSingleExtrusionMachineExtruderDefinition(global_stack)
+            self.fixSingleExtrusionMachineExtruderDefinition(global_stack)
             if extruders_changed:
                 self.extrudersChanged.emit(global_stack_id)
                 self.setActiveExtruderIndex(0)
@@ -349,7 +349,7 @@ class ExtruderManager(QObject):
 
     # After 3.4, all single-extrusion machines have their own extruder definition files instead of reusing
     # "fdmextruder". We need to check a machine here so its extruder definition is correct according to this.
-    def _fixSingleExtrusionMachineExtruderDefinition(self, global_stack: "GlobalStack") -> None:
+    def fixSingleExtrusionMachineExtruderDefinition(self, global_stack: "GlobalStack") -> None:
         container_registry = ContainerRegistry.getInstance()
         expected_extruder_definition_0_id = global_stack.getMetaDataEntry("machine_extruder_trains")["0"]
         extruder_stack_0 = global_stack.extruders.get("0")
diff --git a/cura/Settings/MachineManager.py b/cura/Settings/MachineManager.py
index bb0c0c00ed..bb83a5f25a 100755
--- a/cura/Settings/MachineManager.py
+++ b/cura/Settings/MachineManager.py
@@ -365,7 +365,7 @@ class MachineManager(QObject):
         # Make sure that the default machine actions for this machine have been added
         self._application.getMachineActionManager().addDefaultMachineActions(global_stack)
 
-        ExtruderManager.getInstance()._fixSingleExtrusionMachineExtruderDefinition(global_stack)
+        ExtruderManager.getInstance().fixSingleExtrusionMachineExtruderDefinition(global_stack)
         if not global_stack.isValid():
             # Mark global stack as invalid
             ConfigurationErrorMessage.getInstance().addFaultyContainers(global_stack.getId())
diff --git a/plugins/3MFReader/ThreeMFWorkspaceReader.py b/plugins/3MFReader/ThreeMFWorkspaceReader.py
index bf190f7e39..38652361a5 100755
--- a/plugins/3MFReader/ThreeMFWorkspaceReader.py
+++ b/plugins/3MFReader/ThreeMFWorkspaceReader.py
@@ -26,6 +26,7 @@ from UM.Preferences import Preferences
 
 from cura.Machines.VariantType import VariantType
 from cura.Settings.CuraStackBuilder import CuraStackBuilder
+from cura.Settings.ExtruderManager import ExtruderManager
 from cura.Settings.ExtruderStack import ExtruderStack
 from cura.Settings.GlobalStack import GlobalStack
 from cura.Settings.CuraContainerStack import _ContainerIndexes
@@ -781,6 +782,10 @@ class ThreeMFWorkspaceReader(WorkspaceReader):
             if not quality_changes_info.extruder_info_dict:
                 container_info = ContainerInfo(None, None, None)
                 quality_changes_info.extruder_info_dict["0"] = container_info
+                # If the global stack we're "targeting" has never been active, but was updated from Cura 3.4,
+                # it might not have it's extruders set properly. 
+                if not global_stack.extruders:
+                    ExtruderManager.getInstance().fixSingleExtrusionMachineExtruderDefinition(global_stack)
                 extruder_stack = global_stack.extruders["0"]
 
                 container = quality_manager._createQualityChanges(quality_changes_quality_type, quality_changes_name,