diff -ur mercurial-1.4.1.orig/mercurial/hgweb/hgwebdir_mod.py mercurial-1.4.1/mercurial/hgweb/hgwebdir_mod.py
--- mercurial-1.4.1.orig/mercurial/hgweb/hgwebdir_mod.py	2009-12-02 03:30:45.000000000 +0200
+++ mercurial-1.4.1/mercurial/hgweb/hgwebdir_mod.py	2010-03-06 21:40:34.000000000 +0200
@@ -227,7 +227,7 @@
                 parts = [name]
                 if 'PATH_INFO' in req.env:
                     parts.insert(0, req.env['PATH_INFO'].rstrip('/'))
-                if req.env['SCRIPT_NAME']:
+                if 'SCRIPT_NAME' in req.env:
                     parts.insert(0, req.env['SCRIPT_NAME'])
                 m = re.match('((?:https?://)?)(.*)', '/'.join(parts))
                 # squish repeated slashes out of the path component