diff -r b681d3a2bf04 -r e2b262e2ee73 mercurial/setdiscovery.py
--- a/mercurial/setdiscovery.py	Wed Jan 07 12:09:51 2015 -0800
+++ b/mercurial/setdiscovery.py	Wed Jan 07 17:17:56 2015 -0800
@@ -105,9 +105,10 @@
     return sample
 
 def _takefullsample(dag, nodes, size):
-    always, sample, desiredlen = _setupsample(dag, nodes, size)
-    if sample is None:
+    always = dag.headsetofconnecteds(nodes)
+    if size <= len(always):
         return always
+    sample = set()
     # update from heads
     _updatesample(dag, nodes, sample, always)
     # update from roots