diff -r cd6ae9ab7bd8 -r 84110a1d0f7d mercurial/hgweb/hgweb_mod.py
--- a/mercurial/hgweb/hgweb_mod.py	Sun Mar 11 15:55:38 2018 -0700
+++ b/mercurial/hgweb/hgweb_mod.py	Sun Mar 11 16:19:20 2018 -0700
@@ -312,7 +312,7 @@
 
         # This state is global across all threads.
         encoding.encoding = rctx.config('web', 'encoding')
-        rctx.repo.ui.environ = wsgireq.env
+        rctx.repo.ui.environ = req.rawenv
 
         if rctx.csp:
             # hgwebdir may have added CSP header. Since we generate our own,