diff -r 5f57bc77657c -r 24bb01f42e82 mercurial/exchange.py
--- a/mercurial/exchange.py	Sat Jul 05 19:17:09 2014 +0200
+++ b/mercurial/exchange.py	Sat Jul 05 19:32:20 2014 +0200
@@ -82,7 +82,7 @@
         # phases changes that must be pushed if changeset push fails
         self.fallbackoutdatedphases = None
         # outgoing obsmarkers
-        self.outobsmarkers = repo.obsstore
+        self.outobsmarkers = set()
 
     @util.propertycache
     def futureheads(self):
@@ -278,6 +278,10 @@
     pushop.outdatedphases = future
     pushop.fallbackoutdatedphases = fallback
 
+@pushdiscovery('obsmarker')
+def _pushdiscoveryobsmarkers(pushop):
+    pushop.outobsmarkers = pushop.repo.obsstore
+
 def _pushcheckoutgoing(pushop):
     outgoing = pushop.outgoing
     unfi = pushop.repo.unfiltered()