--- a/mercurial/commands.py	Fri May 13 07:19:59 2016 +0900
+++ b/mercurial/commands.py	Fri May 13 07:19:59 2016 +0900
@@ -4590,7 +4590,7 @@
     subtopic = None
     if name and '.' in name:
         name, section = name.split('.', 1)
-        section = section.lower()
+        section = encoding.lower(section)
         if '.' in section:
             subtopic, section = section.split('.', 1)
         else: