--- a/mercurial/hgweb/hgweb_mod.py	Sun Mar 18 15:14:58 2018 +0900
+++ b/mercurial/hgweb/hgweb_mod.py	Sun Mar 18 15:42:28 2018 +0900
@@ -173,7 +173,7 @@
 
         filters = {}
         templatefilter = registrar.templatefilter(filters)
-        @templatefilter('websub')
+        @templatefilter('websub', intype=bytes)
         def websubfilter(text):
             return templatefilters.websub(text, self.websubtable)