diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 7ad741848e..35fd724ddd 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -1030,8 +1030,10 @@ class OPF(object): # {{{
             attrib = attrib or {}
             attrib['name'] = 'calibre:' + name
             name = '{%s}%s' % (self.NAMESPACES['opf'], 'meta')
+        nsmap = dict(self.NAMESPACES)
+        del nsmap['opf']
         elem = etree.SubElement(self.metadata, name, attrib=attrib,
-                                nsmap=self.NAMESPACES)
+                                nsmap=nsmap)
         elem.tail = '\n'
         return elem