diff --git a/hgext/lfs/wrapper.py b/hgext/lfs/wrapper.py
--- a/hgext/lfs/wrapper.py
+++ b/hgext/lfs/wrapper.py
@@ -524,7 +524,7 @@
     remoteblob.writebatch(pointers, repo.svfs.lfslocalblobstore)
 
 
-@eh.wrapfunction(upgrade_engine, b'_finishdatamigration')
+@eh.wrapfunction(upgrade_engine, b'finishdatamigration')
 def upgradefinishdatamigration(orig, ui, srcrepo, dstrepo, requirements):
     orig(ui, srcrepo, dstrepo, requirements)
 
diff --git a/mercurial/upgrade_utils/engine.py b/mercurial/upgrade_utils/engine.py
--- a/mercurial/upgrade_utils/engine.py
+++ b/mercurial/upgrade_utils/engine.py
@@ -408,7 +408,7 @@
     return True
 
 
-def _finishdatamigration(ui, srcrepo, dstrepo, requirements):
+def finishdatamigration(ui, srcrepo, dstrepo, requirements):
     """Hook point for extensions to perform additional actions during upgrade.
 
     This function is called after revlogs and store files have been copied but
@@ -458,7 +458,7 @@
         dst = dstrepo.store.rawvfs.join(p)
         util.copyfile(src, dst, copystat=True)
 
-    _finishdatamigration(ui, srcrepo, dstrepo, requirements)
+    finishdatamigration(ui, srcrepo, dstrepo, requirements)
 
     ui.status(_(b'data fully migrated to temporary repository\n'))