diff -r 0194dac77c93 -r 7d3bc1d4e871 mercurial/templater.py
--- a/mercurial/templater.py	Mon Apr 02 16:18:33 2018 -0700
+++ b/mercurial/templater.py	Sat Mar 17 20:09:05 2018 +0900
@@ -679,7 +679,7 @@
         if extramapping:
             extramapping.update(mapping)
             mapping = extramapping
-        return templateutil.flatten(func(self, mapping, data))
+        return templateutil.flatten(self, mapping, func(self, mapping, data))
 
 engines = {'default': engine}