diff --git a/src/calibre/ebooks/oeb/polish/toc.py b/src/calibre/ebooks/oeb/polish/toc.py
index bcca0b9991..0a5744f64b 100644
--- a/src/calibre/ebooks/oeb/polish/toc.py
+++ b/src/calibre/ebooks/oeb/polish/toc.py
@@ -422,7 +422,7 @@ def create_ncx(toc, to_href, btitle, lang, uid):
     def process_node(xml_parent, toc_parent):
         for child in toc_parent:
             play_order['c'] += 1
-            point = etree.SubElement(xml_parent, NCX('navPoint'), id=uuid_id(),
+            point = etree.SubElement(xml_parent, NCX('navPoint'), id='num_%d' % play_order['c'],
                             playOrder=str(play_order['c']))
             label = etree.SubElement(point, NCX('navLabel'))
             title = child.title