diff -r b9b968e21f78 -r ec46415ed826 mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py	Thu Mar 08 15:15:59 2018 -0800
+++ b/mercurial/hgweb/hgweb_mod.py	Thu Mar 08 15:14:32 2018 -0800
@@ -177,8 +177,7 @@
         if style == styles[0]:
             vars['style'] = style
 
-        start = '&' if wsgireq.url[-1] == r'?' else '?'
-        sessionvars = webutil.sessionvars(vars, start)
+        sessionvars = webutil.sessionvars(vars, '?')
 
         if not self.reponame:
             self.reponame = (self.config('web', 'name', '')