diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -11,8 +11,9 @@
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
-import os
+from demandload import demandload
 from i18n import gettext as _
+demandload(globals(), 'os')
 
 class transaction(object):
     def __init__(self, report, opener, journal, after=None):