diff --git a/ironic/db/sqlalchemy/api.py b/ironic/db/sqlalchemy/api.py
index d4b8f868d9..c2c39f0ccd 100644
--- a/ironic/db/sqlalchemy/api.py
+++ b/ironic/db/sqlalchemy/api.py
@@ -1218,11 +1218,18 @@ class Connection(api.Connection):
                     ids = []
                     for obj in query.slice(0, max_to_migrate):
                         ids.append(obj['id'])
-                    query = model_query(model).filter(model.id.in_(ids))
-
-                num_migrated = query.update(
-                    {model.version: mapping[model.__name__][0]},
-                    synchronize_session=False)
+                    num_migrated = (
+                        model_query(model).
+                        filter(sql.and_(model.id.in_(ids),
+                                        model.version.is_(None))).
+                        update({model.version: mapping[model.__name__][0]},
+                               synchronize_session=False))
+                else:
+                    num_migrated = (
+                        model_query(model).
+                        filter(model.version.is_(None)).
+                        update({model.version: mapping[model.__name__][0]},
+                               synchronize_session=False))
 
             total_migrated += num_migrated
             max_to_migrate -= num_migrated
diff --git a/releasenotes/notes/backfill_version_column_db_race_condition-713fa05832b93ca5.yaml b/releasenotes/notes/backfill_version_column_db_race_condition-713fa05832b93ca5.yaml
new file mode 100644
index 0000000000..febe06281f
--- /dev/null
+++ b/releasenotes/notes/backfill_version_column_db_race_condition-713fa05832b93ca5.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixes an issue when running ``ironic-dbsync online_data_migrations``. The
+    value of an object's new ``version`` column might have been incorrectly
+    changed from a newer object version to an older object version, due to a
+    race condition. This is no longer the case.