--- a/mercurial/hgweb/server.py	Fri Jun 30 03:45:48 2017 +0200
+++ b/mercurial/hgweb/server.py	Fri Jun 30 03:45:49 2017 +0200
@@ -277,7 +277,7 @@
 
         handler.preparehttpserver(self, ui)
 
-        prefix = ui.config('web', 'prefix', '')
+        prefix = ui.config('web', 'prefix')
         if prefix:
             prefix = '/' + prefix.strip('/')
         self.prefix = prefix