diff --git a/app/celery/letters_pdf_tasks.py b/app/celery/letters_pdf_tasks.py
index 5f715c97d..75c2e5c62 100644
--- a/app/celery/letters_pdf_tasks.py
+++ b/app/celery/letters_pdf_tasks.py
@@ -182,15 +182,15 @@ def get_key_and_size_of_letters_to_be_sent_to_print(print_run_deadline, postage)
         try:
             letter_file_name = get_letter_pdf_filename(
                 reference=letter.reference,
-                crown=letter.service.crown,
+                crown=letter.crown,
                 created_at=letter.created_at,
-                postage=letter.postage
+                postage=postage
             )
             letter_head = s3.head_s3_object(current_app.config['LETTERS_PDF_BUCKET_NAME'], letter_file_name)
             yield {
                 "Key": letter_file_name,
                 "Size": letter_head['ContentLength'],
-                "ServiceId": str(letter.service.id)
+                "ServiceId": str(letter.service_id)
             }
         except BotoClientError as e:
             current_app.logger.exception(
diff --git a/app/dao/notifications_dao.py b/app/dao/notifications_dao.py
index 7c8564489..5346ed63a 100644
--- a/app/dao/notifications_dao.py
+++ b/app/dao/notifications_dao.py
@@ -721,7 +721,15 @@ def dao_get_letters_to_be_printed(print_run_deadline, postage):
     """
     Return all letters created before the print run deadline that have not yet been sent
     """
-    notifications = Notification.query.filter(
+    notifications = db.session.query(
+        Notification.id,
+        Notification.created_at,
+        Notification.reference,
+        Notification.service_id,
+        Service.crown,
+    ).join(
+        Notification.service
+    ).filter(
         Notification.created_at < convert_bst_to_utc(print_run_deadline),
         Notification.notification_type == LETTER_TYPE,
         Notification.status == NOTIFICATION_CREATED,
diff --git a/tests/app/dao/notification_dao/test_notification_dao.py b/tests/app/dao/notification_dao/test_notification_dao.py
index 8b8717740..3e74ca0e9 100644
--- a/tests/app/dao/notification_dao/test_notification_dao.py
+++ b/tests/app/dao/notification_dao/test_notification_dao.py
@@ -1694,4 +1694,4 @@ def test_letters_to_be_printed_sort_by_service(notify_db_session):
 
     results = list(dao_get_letters_to_be_printed(print_run_deadline=datetime(2020, 12, 1, 17, 30), postage='second'))
     assert len(results) == 3
-    assert results == [notification_1, notification_2, notification_3]
+    assert [x.id for x in results] == [notification_1.id, notification_2.id, notification_3.id]