diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index 08fec4479e4..508c36bf7c6 100755
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -187,7 +187,7 @@ def __init__(self, *args, **kwargs):
 
         self._cura_formula_functions = None  # type: Optional[CuraFormulaFunctions]
 
-        self._machine_action_manager = None  # type: Optional[MachineActionManager]
+        self._machine_action_manager: Optional[MachineActionManager] = None
 
         self.empty_container = None  # type: EmptyInstanceContainer
         self.empty_definition_changes_container = None  # type: EmptyInstanceContainer