diff -r b4630e332a99 -r 9e8128e84326 mercurial/templatefuncs.py
--- a/mercurial/templatefuncs.py	Sat Mar 17 20:58:28 2018 +0900
+++ b/mercurial/templatefuncs.py	Sun Mar 18 23:14:21 2018 +0900
@@ -319,7 +319,7 @@
     # TODO: perhaps this should be evalfuncarg(), but it can't because hgweb
     # abuses generator as a keyword that returns a list of dicts.
     joinset = evalrawexp(context, mapping, args[0])
-    joinset = templateutil.unwrapvalue(joinset)
+    joinset = templateutil.unwrapvalue(context, mapping, joinset)
     joinfmt = getattr(joinset, 'joinfmt', pycompat.identity)
     joiner = " "
     if len(args) > 1: