--- a/mercurial/hgweb/webutil.py	Mon Sep 09 17:26:17 2019 -0400
+++ b/mercurial/hgweb/webutil.py	Mon Sep 09 13:25:00 2019 -0400
@@ -791,7 +791,7 @@
         flagin = match.group(3)
         flags = 0
         if flagin:
-            for flag in flagin.upper():
+            for flag in pycompat.sysstr(flagin.upper()):
                 flags |= re.__dict__[flag]
 
         try: