diff -r f00a63a43c4b -r d410336fdb3c mercurial/exchange.py
--- a/mercurial/exchange.py	Mon Jun 08 13:32:38 2015 -0700
+++ b/mercurial/exchange.py	Wed May 27 05:35:00 2015 -0700
@@ -523,7 +523,7 @@
     part2node = []
     enc = pushkey.encode
     for newremotehead in pushop.outdatedphases:
-        part = bundler.newpart('pushkey')
+        part = bundler.newpart('pushkey', mandatory=False)
         part.addparam('namespace', enc('phases'))
         part.addparam('key', enc(newremotehead.hex()))
         part.addparam('old', enc(str(phases.draft)))
@@ -567,7 +567,7 @@
     part2book = []
     enc = pushkey.encode
     for book, old, new in pushop.outbookmarks:
-        part = bundler.newpart('pushkey')
+        part = bundler.newpart('pushkey', mandatory=False)
         part.addparam('namespace', enc('bookmarks'))
         part.addparam('key', enc(book))
         part.addparam('old', enc(old))