diff --git a/backend/postcode_splitter/main.py b/backend/postcode_splitter/main.py
index 930fac7f..e49a7f0d 100644
--- a/backend/postcode_splitter/main.py
+++ b/backend/postcode_splitter/main.py
@@ -136,7 +136,7 @@ def create_batch_and_send_to_address2uprn(
     # Send message with S3 reference
     send_to_address2uprn_queue(
         task_id=str(task_id),
-        sub_task_id=batch_sub_task_id,
+        sub_task_id=created_batch_sub_task_id,
         s3_uri=s3_uri,
     )