diff --git a/src/calibre/ebooks/metadata/opf.xml b/src/calibre/ebooks/metadata/opf.xml
index 10623715ff..3a6cfec58c 100644
--- a/src/calibre/ebooks/metadata/opf.xml
+++ b/src/calibre/ebooks/metadata/opf.xml
@@ -1,14 +1,14 @@
 <?xml version="1.0"  encoding="UTF-8"?>
 <package version="2.0" 
-         xmlns:opf="http://www.idpf.org/2007/opf" 
+         xmlns="http://www.idpf.org/2007/opf" 
          xmlns:py="http://genshi.edgewall.org/" 
          unique-identifier="${__appname__}_id"
          
 >
-    <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
-        <dc:title py:with="attrs={'files-as':mi.title_sort}" py:attrs="attrs">${mi.title}</dc:title>
-        <dc:creator opf:role="aut" py:for="i, author in enumerate(mi.authors)" py:with="attrs={'file-as':mi.author_sort if i==0 else None}" py:attrs="attrs">${author}</dc:creator>
-        <dc:identifier scheme="${__appname__}" id="${__appname__}_id">${mi.application_id}</dc:identifier>
+    <metadata xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:opf="http://www.idpf.org/2007/opf">
+        <dc:title py:with="attrs={'opf:files-as':mi.title_sort}" py:attrs="attrs">${mi.title}</dc:title>
+        <dc:creator opf:role="aut" py:for="i, author in enumerate(mi.authors)" py:with="attrs={'opf:file-as':mi.author_sort if i==0 else None}" py:attrs="attrs">${author}</dc:creator>
+        <dc:identifier opf:scheme="${__appname__}" id="${__appname__}_id">${mi.application_id}</dc:identifier>
     
         <dc:language>${mi.language if mi.language else 'Unknown'}</dc:language>
         <dc:type py:if="mi.category">${mi.category}</dc:type>
diff --git a/src/calibre/utils/genshi/output.py b/src/calibre/utils/genshi/output.py
index d07d3f72b0..3664d92f37 100644
--- a/src/calibre/utils/genshi/output.py
+++ b/src/calibre/utils/genshi/output.py
@@ -573,6 +573,7 @@ class NamespaceFlattener(object):
     def __call__(self, stream):
         prefixes = dict([(v, [k]) for k, v in self.prefixes.items()])
         namespaces = {XML_NAMESPACE.uri: ['xml']}
+        default = prefixes.get('', [''])
         def _push_ns(prefix, uri):
             namespaces.setdefault(uri, []).append(prefix)
             prefixes.setdefault(prefix, []).append(uri)
@@ -596,14 +597,14 @@ class NamespaceFlattener(object):
 
                 tagname = tag.localname
                 tagns = tag.namespace
-                if tagns:
+                if tagns and tagns != default[-1]:
                     if tagns in namespaces:
                         prefix = namespaces[tagns][-1]
                         if prefix:
                             tagname = u'%s:%s' % (prefix, tagname)
                     else:
                         _push_ns_attr((u'xmlns', tagns))
-                        _push_ns('', tagns)
+                        default.push(tagns)
 
                 new_attrs = []
                 for attr, value in attrs:
@@ -626,7 +627,7 @@ class NamespaceFlattener(object):
             elif kind is END:
                 tagname = data.localname
                 tagns = data.namespace
-                if tagns:
+                if tagns and tagns != default[-1]:
                     prefix = namespaces[tagns][-1]
                     if prefix:
                         tagname = u'%s:%s' % (prefix, tagname)
@@ -634,12 +635,19 @@ class NamespaceFlattener(object):
 
             elif kind is START_NS:
                 prefix, uri = data
-                if uri not in namespaces:
-                    prefix = prefixes.get(uri, [prefix])[-1]
+                push_attr = False
+                if prefix is '' and default[-1] != uri:
+                    default.append(uri)
                     _push_ns_attr(_make_ns_attr(prefix, uri))
-                _push_ns(prefix, uri)
+                elif uri not in namespaces:
+                    prefix = namespaces.get(uri, [prefix])[-1]
+                    _push_ns_attr(_make_ns_attr(prefix, uri))
+                if prefix is not '':
+                    _push_ns(prefix, uri)
 
             elif kind is END_NS:
+                if data is '':
+                    default.pop()
                 if data in prefixes:
                     uris = prefixes.get(data)
                     uri = uris.pop()