--- a/mercurial/hgweb/webcommands.py	Mon Jan 08 11:11:06 2018 +0900
+++ b/mercurial/hgweb/webcommands.py	Sun Dec 27 13:08:51 2015 +0900
@@ -1403,7 +1403,7 @@
 
     try:
         doc = helpmod.help_(u, commands, topic, subtopic=subtopic)
-    except error.UnknownCommand:
+    except error.Abort:
         raise ErrorResponse(HTTP_NOT_FOUND)
     return tmpl('help', topic=topicname, doc=doc)