diff --git a/freecad/silo_origin.py b/freecad/silo_origin.py
index e839551..5efe09c 100644
--- a/freecad/silo_origin.py
+++ b/freecad/silo_origin.py
@@ -392,8 +392,10 @@ class SiloOrigin:
                 obj.SiloPartNumber, str(file_path), properties, comment=""
             )
 
-            # Clear modified flag
-            doc.Modified = False
+            # Clear modified flag (Modified is on Gui.Document, not App.Document)
+            gui_doc = FreeCADGui.getDocument(doc.Name)
+            if gui_doc:
+                gui_doc.Modified = False
 
             return True
         except Exception as e: