diff --git a/mercurial/hgweb/hgweb_mod.py b/mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py
+++ b/mercurial/hgweb/hgweb_mod.py
@@ -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', '')
diff --git a/mercurial/hgweb/hgwebdir_mod.py b/mercurial/hgweb/hgwebdir_mod.py
--- a/mercurial/hgweb/hgwebdir_mod.py
+++ b/mercurial/hgweb/hgwebdir_mod.py
@@ -509,8 +509,7 @@
         if style == styles[0]:
             vars['style'] = style
 
-        start = r'&' if url[-1] == r'?' else r'?'
-        sessionvars = webutil.sessionvars(vars, start)
+        sessionvars = webutil.sessionvars(vars, r'?')
         logourl = config('web', 'logourl')
         logoimg = config('web', 'logoimg')
         staticurl = config('web', 'staticurl') or url + 'static/'