diff -r 95791b275b73 -r 788b2e8530ae mercurial/archival.py
--- a/mercurial/archival.py	Sun Feb 11 10:49:00 2018 -0800
+++ b/mercurial/archival.py	Sun Feb 11 10:52:13 2018 -0800
@@ -218,7 +218,7 @@
                 dest.tell()
             except (AttributeError, IOError):
                 dest = tellable(dest)
-        self.z = zipfile.ZipFile(dest, 'w',
+        self.z = zipfile.ZipFile(dest, r'w',
                                  compress and zipfile.ZIP_DEFLATED or
                                  zipfile.ZIP_STORED)