diff --git a/product/ERP5Type/CopySupport.py b/product/ERP5Type/CopySupport.py
index 17e49467b4f55f7ee282e7891a1e5543a32fd49d..97c759c17f93a0c6983e70d6f026de1ce2bc7848 100644
--- a/product/ERP5Type/CopySupport.py
+++ b/product/ERP5Type/CopySupport.py
@@ -355,8 +355,10 @@ class CopyContainer:
           # Set also many columns in order to make sure lines
           # marked as deleted will not be selected
           catalog.beforeUnindexObject(None,path=path,uid=uid)
-          # Then start activty in order to remove lines in catalog,
+          # Then start activity in order to remove lines in catalog,
           # sql wich generate locks
+          # - serialization_tag is used in order to prevent unindexation to 
+          # happen before/in parallel with reindexations of the same object.
           catalog.activate(activity='SQLQueue',
                            tag='%s' % uid,
                            serialization_tag=self.getRootDocumentPath()).unindexObject(None,