diff --git a/src/calibre/library/server/content.py b/src/calibre/library/server/content.py
index ecb467b4c2..95794a8c1d 100644
--- a/src/calibre/library/server/content.py
+++ b/src/calibre/library/server/content.py
@@ -56,7 +56,7 @@ class ContentServer(object):
 
     def sort(self, items, field, order):
         field = self.db.data.sanitize_sort_field_name(field)
-        if field not in ('title', 'authors', 'rating', 'timestamp', 'tags', 'size', 'series'):
+        if field not in self.db.field_metadata.field_keys():
             raise cherrypy.HTTPError(400, '%s is not a valid sort field'%field)
         keyg = CSSortKeyGenerator([(field, order)], self.db.field_metadata)
         items.sort(key=keyg, reverse=not order)