diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 9389964962..ccc452f1f8 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -515,7 +515,7 @@ class Metadata(object):
                          'publisher', 'relation', 'rights', 'source',
                          'subject', 'title', 'type'])
     CALIBRE_TERMS = set(['series', 'series_index', 'rating', 'timestamp',
-                         'publication_type'])
+                         'publication_type', 'title_sort'])
     OPF_ATTRS     = {'role': OPF('role'), 'file-as': OPF('file-as'),
                      'scheme': OPF('scheme'), 'event': OPF('event'),
                      'type': XSI('type'), 'lang': XML('lang'), 'id': 'id'}
diff --git a/src/calibre/ebooks/oeb/transforms/metadata.py b/src/calibre/ebooks/oeb/transforms/metadata.py
index f1ce31f25b..19c209b74d 100644
--- a/src/calibre/ebooks/oeb/transforms/metadata.py
+++ b/src/calibre/ebooks/oeb/transforms/metadata.py
@@ -18,7 +18,8 @@ def meta_info_to_oeb_metadata(mi, m, log, override_input_metadata=False):
     if mi.title_sort:
         if not m.title:
             m.add('title', mi.title_sort)
-        m.title[0].file_as = mi.title_sort
+        m.clear('title_sort')
+        m.add('title_sort', mi.title_sort)
     if not mi.is_null('authors'):
         m.filter('creator', lambda x : x.role.lower() in ['aut', ''])
         for a in mi.authors: