diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index 24d73f465e..42a6b7f960 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -369,6 +369,7 @@ class MyBlockingBusy(QDialog):  # {{{
         if args.clear_series:
             self.progress_next_step_range.emit(0)
             cache.set_field('series', {bid: '' for bid in self.ids})
+            cache.set_field('series_index', {bid:1.0 for bid in self.ids})
             self.progress_finished_cur_step.emit()
 
         if args.pubdate is not None: