--- a/mercurial/templater.py	Wed Apr 10 02:27:35 2013 +0900
+++ b/mercurial/templater.py	Tue Apr 16 09:44:29 2013 -0500
@@ -228,7 +228,8 @@
 
     joinset = args[0][0](context, mapping, args[0][1])
     if util.safehasattr(joinset, '__call__'):
-        joinset = [x.values()[0] for x in joinset()]
+        jf = joinset.joinfmt
+        joinset = [jf(x) for x in joinset()]
 
     joiner = " "
     if len(args) > 1: