diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst
index 458f746..9ce781e 100644
--- a/Doc/library/xml.etree.elementtree.rst
+++ b/Doc/library/xml.etree.elementtree.rst
@@ -767,13 +767,15 @@
       root element.
 
 
-   .. method:: write(file, encoding="us-ascii", xml_declaration=None, method="xml")
+   .. method:: write(file, encoding="us-ascii", xml_declaration=None, \
+                     default_namespace=None, method="xml")
 
       Writes the element tree to a file, as XML.  *file* is a file name, or a
       file object opened for writing.  *encoding* [1]_ is the output encoding
       (default is US-ASCII).  *xml_declaration* controls if an XML declaration
       should be added to the file.  Use False for never, True for always, None
-      for only if not US-ASCII or UTF-8 (default is None).  *method* is either
+      for only if not US-ASCII or UTF-8 (default is None).  *default_namespace*
+      sets the default XML namespace (for "xmlns").  *method* is either
       ``"xml"``, ``"html"`` or ``"text"`` (default is ``"xml"``).  Returns an
       encoded string.
 
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index d8ec67a..cd33cd0 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -779,11 +779,12 @@
     # @param file A file name, or a file object opened for writing.
     # @param **options Options, given as keyword arguments.
     # @keyparam encoding Optional output encoding (default is US-ASCII).
-    # @keyparam method Optional output method ("xml", "html", "text" or
-    #     "c14n"; default is "xml").
     # @keyparam xml_declaration Controls if an XML declaration should
     #     be added to the file.  Use False for never, True for always,
     #     None for only if not US-ASCII or UTF-8.  None is default.
+    # @keyparam default_namespace Sets the default XML namespace (for "xmlns").
+    # @keyparam method Optional output method ("xml", "html", "text" or
+    #     "c14n"; default is "xml").
 
     def write(self, file_or_filename,
               # keyword arguments