diff --git a/sleekxmpp/xmlstream/stanzabase.py b/sleekxmpp/xmlstream/stanzabase.py
index abe0abdc..233e91f6 100644
--- a/sleekxmpp/xmlstream/stanzabase.py
+++ b/sleekxmpp/xmlstream/stanzabase.py
@@ -1400,10 +1400,8 @@ class ElementBase(object):
         :param bool top_level_ns: Display the top-most namespace.
                                   Defaults to True.
         """
-        stanza_ns = '' if top_level_ns else self.namespace
         return tostring(self.xml, xmlns='',
-                        stanza_ns=stanza_ns,
-                        top_level=not top_level_ns)
+                        top_level=True)
 
     def __repr__(self):
         """Use the stanza's serialized XML as its representation."""
@@ -1592,11 +1590,10 @@ class StanzaBase(ElementBase):
         :param bool top_level_ns: Display the top-most namespace.
                                   Defaults to ``False``.
         """
-        stanza_ns = '' if top_level_ns else self.namespace
-        return tostring(self.xml, xmlns='',
-                        stanza_ns=stanza_ns,
+        xmlns = self.stream.default_ns if self.stream else ''
+        return tostring(self.xml, xmlns=xmlns,
                         stream=self.stream,
-                        top_level=not top_level_ns)
+                        top_level=(self.stream is None))
 
 
 #: A JSON/dictionary version of the XML content exposed through
diff --git a/sleekxmpp/xmlstream/tostring.py b/sleekxmpp/xmlstream/tostring.py
index f22e7770..0b73d8dc 100644
--- a/sleekxmpp/xmlstream/tostring.py
+++ b/sleekxmpp/xmlstream/tostring.py
@@ -24,19 +24,18 @@ if sys.version_info < (3, 0):
 XML_NS = 'http://www.w3.org/XML/1998/namespace'
 
 
-def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
+def tostring(xml=None, xmlns='', stream=None,
              outbuffer='', top_level=False, open_only=False):
     """Serialize an XML object to a Unicode string.
 
-    If namespaces are provided using ``xmlns`` or ``stanza_ns``, then
-    elements that use those namespaces will not include the xmlns attribute
-    in the output.
+    If an outer xmlns is provided using ``xmlns``, then the current element's
+    namespace will not be included if it matches the outer namespace. An
+    exception is made for elements that have an attached stream, and appear
+    at the stream root.
 
     :param XML xml: The XML object to serialize.
     :param string xmlns: Optional namespace of an element wrapping the XML
                          object.
-    :param string stanza_ns: The namespace of the stanza object that contains
-                             the XML object.
     :param stream: The XML stream that generated the XML object.
     :param string outbuffer: Optional buffer for storing serializations
                              during recursive calls.
@@ -71,8 +70,8 @@ def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
 
     # Output the tag name and derived namespace of the element.
     namespace = ''
-    if top_level and tag_xmlns not in ['', default_ns, stream_ns] or \
-            tag_xmlns not in ['', xmlns, stanza_ns, stream_ns]:
+    if top_level and tag_xmlns not in [default_ns, xmlns, stream_ns] \
+      or not top_level and tag_xmlns != xmlns:
         namespace = ' xmlns="%s"' % tag_xmlns
     if stream and tag_xmlns in stream.namespace_map:
         mapped_namespace = stream.namespace_map[tag_xmlns]
@@ -110,7 +109,7 @@ def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
             output.append(escape(xml.text, use_cdata))
         if len(xml):
             for child in xml:
-                output.append(tostring(child, tag_xmlns, stanza_ns, stream))
+                output.append(tostring(child, tag_xmlns, stream))
         output.append("</%s>" % tag_name)
     elif xml.text:
         # If we only have text content.
diff --git a/sleekxmpp/xmlstream/xmlstream.py b/sleekxmpp/xmlstream/xmlstream.py
index a58b63d4..dff32461 100644
--- a/sleekxmpp/xmlstream/xmlstream.py
+++ b/sleekxmpp/xmlstream/xmlstream.py
@@ -1244,7 +1244,9 @@ class XMLStream(object):
                         data = filter(data)
                         if data is None:
                             return
-                str_data = str(data)
+                str_data = tostring(data.xml, xmlns=self.default_ns,
+                                              stream=self,
+                                              top_level=True)
                 self.send_raw(str_data, now)
         else:
             self.send_raw(data, now)
diff --git a/tests/test_tostring.py b/tests/test_tostring.py
index cd50a7c1..8c04f00c 100644
--- a/tests/test_tostring.py
+++ b/tests/test_tostring.py
@@ -85,19 +85,6 @@ class TestToString(SleekTest):
             original='<a>foo <b>bar</b> baz</a>',
             message='Element tail content is incorrect.')
 
-
-    def testStanzaNs(self):
-        """
-        Test using the stanza_ns tostring parameter, which will prevent
-        adding an xmlns attribute to the serialized element if the
-        element's namespace is the same.
-        """
-        self.tryTostring(
-            original='<bar xmlns="foo" />',
-            expected='<bar />',
-            message="The stanza_ns parameter was not used properly.",
-            stanza_ns='foo')
-
     def testStanzaStr(self):
         """
         Test that stanza objects are serialized properly.