diff --git a/cura/Settings/ExtruderStack.py b/cura/Settings/ExtruderStack.py
index e7f57eb4ef..6484692439 100644
--- a/cura/Settings/ExtruderStack.py
+++ b/cura/Settings/ExtruderStack.py
@@ -20,7 +20,7 @@ if TYPE_CHECKING:
 #
 #
 class ExtruderStack(CuraContainerStack):
-    def __init__(self, container_id, *args, **kwargs):
+    def __init__(self, container_id: str, *args, **kwargs):
         super().__init__(container_id, *args, **kwargs)
 
         self.addMetaDataEntry("type", "extruder_train") # For backward compatibility