diff --git a/jeepyb/cmd/update_bug.py b/jeepyb/cmd/update_bug.py
index 4f78ca4..43bd6c2 100644
--- a/jeepyb/cmd/update_bug.py
+++ b/jeepyb/cmd/update_bug.py
@@ -206,6 +206,7 @@
     """Apply changes to lp bug tasks, based on hook / branch."""
 
     bugtask = task.lp_task
+    series = None
 
     if args.hook == "change-abandoned":
         add_change_abandoned_message(bugtask, args.change_url,