diff --git a/mercurial/hgweb/__init__.py b/mercurial/hgweb/__init__.py
--- a/mercurial/hgweb/__init__.py
+++ b/mercurial/hgweb/__init__.py
@@ -38,7 +38,7 @@
     - list of virtual:real tuples (multi-repo view)
     '''
 
-    if ((isinstance(config, str) and not os.path.isdir(config)) or
+    if ((isinstance(config, bytes) and not os.path.isdir(config)) or
         isinstance(config, dict) or isinstance(config, list)):
         # create a multi-dir interface
         return hgwebdir_mod.hgwebdir(config, baseui=baseui)