From d239e0907e6a4326e1710f9da43a4529962d51c2 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 9 Nov 2012 12:42:20 +0530
Subject: [PATCH] ...

---
 src/calibre/ebooks/oeb/transforms/subset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/calibre/ebooks/oeb/transforms/subset.py b/src/calibre/ebooks/oeb/transforms/subset.py
index 9b10aaad06..f85f786547 100644
--- a/src/calibre/ebooks/oeb/transforms/subset.py
+++ b/src/calibre/ebooks/oeb/transforms/subset.py
@@ -89,7 +89,7 @@ class SubsetFonts(object):
             except (IndexError, KeyError, AttributeError, TypeError, ValueError):
                 val = None if q in {'src', 'font-family'} else default
             if q in {'font-weight', 'font-stretch', 'font-style'}:
-                val = val.lower() if val else val
+                val = unicode(val).lower() if (val or val == 0) else val
                 if val == 'inherit':
                     val = default
             if q == 'font-weight':