diff --git a/src/calibre/ebooks/conversion/plugins/html_output.py b/src/calibre/ebooks/conversion/plugins/html_output.py
index 3821ba41a4..68d32d1aec 100644
--- a/src/calibre/ebooks/conversion/plugins/html_output.py
+++ b/src/calibre/ebooks/conversion/plugins/html_output.py
@@ -4,12 +4,15 @@ __copyright__ = '2010, Fabian Grassl <fg@jusmeum.de>'
 __docformat__ = 'restructuredtext en'
 
 import os, re, shutil
-from os.path import dirname, abspath, relpath, exists, basename
+from os.path import dirname, abspath, relpath as _relpath, exists, basename
 
 from calibre.customize.conversion import OutputFormatPlugin, OptionRecommendation
 from calibre import CurrentDir
 from calibre.ptempfile import PersistentTemporaryDirectory
 
+def relpath(*args):
+    return _relpath(*args).replace(os.sep, '/')
+
 class HTMLOutput(OutputFormatPlugin):
 
     name = 'HTML Output'