diff --git a/src/documents/bulk_edit.py b/src/documents/bulk_edit.py
index 047ddbf0c..17dbfa760 100644
--- a/src/documents/bulk_edit.py
+++ b/src/documents/bulk_edit.py
@@ -667,7 +667,7 @@ def merge_as_versions(
         for source_id in source_ids:
             next_version_index += 1
             updates = {
-                "root_document": root_document,
+                "root_document_id": root_document.pk,
                 "version_index": next_version_index,
                 "archive_serial_number": None,
             }