--- a/mercurial/commands.py	Thu Jun 15 23:09:14 2017 -0700
+++ b/mercurial/commands.py	Thu Jun 15 22:46:38 2017 -0700
@@ -5339,8 +5339,8 @@
                 modheads = changegroup.combineresults(changes)
             else:
                 txnname = 'unbundle\n%s' % util.hidepassword(url)
-                with repo.transaction(txnname):
-                    modheads = gen.apply(repo, 'unbundle', url)
+                with repo.transaction(txnname) as tr:
+                    modheads = gen.apply(repo, tr, 'unbundle', url)
 
     return postincoming(ui, repo, modheads, opts.get(r'update'), None, None)