--- a/mercurial/templatekw.py	Tue Jun 20 22:11:46 2017 +0530
+++ b/mercurial/templatekw.py	Tue Jun 20 23:46:18 2017 +0530
@@ -126,7 +126,7 @@
             yield templ(noname, **mapping)
         return
     if name not in templ:
-        if isinstance(values[0], str):
+        if isinstance(values[0], bytes):
             yield separator.join(values)
         else:
             for v in values: