diff --git a/mercurial/exchange.py b/mercurial/exchange.py
index baecf4e1b7d02f62b368515bf07f5239b10ab9b9_bWVyY3VyaWFsL2V4Y2hhbmdlLnB5..827bce9e24fba5ed39043a35e842a07b8479a83f_bWVyY3VyaWFsL2V4Y2hhbmdlLnB5 100644
--- a/mercurial/exchange.py
+++ b/mercurial/exchange.py
@@ -618,7 +618,7 @@
     remote = pushop.remote
     ui.debug("checking for updated bookmarks\n")
     revnums = map(repo.changelog.rev, pushop.revs or [])
-    ancestors = [a for a in repo.changelog.ancestors(revnums, inclusive=True)]
+    ancestors = repo.changelog.ancestors(revnums, inclusive=True)
     (addsrc, adddst, advsrc, advdst, diverge, differ, invalid
      ) = bookmarks.compare(repo, repo._bookmarks, remote.listkeys('bookmarks'),
                            srchex=hex)