diff --git a/src/calibre/gui2/toc/main.py b/src/calibre/gui2/toc/main.py
index 50219f7aa2..78accb976f 100644
--- a/src/calibre/gui2/toc/main.py
+++ b/src/calibre/gui2/toc/main.py
@@ -628,8 +628,8 @@ class TreeWidget(QTreeWidget):  # {{{
 
     def bulk_rename(self):
         from calibre.gui2.tweak_book.file_list import get_bulk_rename_settings
-        sort_map = {item:i for i, item in enumerate(self.iter_items())}
-        items = sorted(self.selectedItems(), key=lambda x:sort_map.get(x, -1))
+        sort_map = {id(item):i for i, item in enumerate(self.iter_items())}
+        items = sorted(self.selectedItems(), key=lambda x:sort_map.get(id(x), -1))
         settings = get_bulk_rename_settings(self, len(items), prefix=_('Chapter '), msg=_(
             'All selected items will be renamed to the form prefix-number'), sanitize=lambda x:x, leading_zeros=False)
         fmt, num = settings['prefix'], settings['start']