diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst
index 26f1fbe7a17..144e344397a 100644
--- a/Doc/library/xml.etree.elementtree.rst
+++ b/Doc/library/xml.etree.elementtree.rst
@@ -742,7 +742,7 @@ ElementTree Objects
 
 
    .. method:: write(file, encoding="us-ascii", xml_declaration=None, \
-                     method="xml")
+                     default_namespace=None, method="xml")
 
       Writes the element tree to a file, as XML.  *file* is a file name, or a
       :term:`file object` opened for writing.  *encoding* [1]_ is the output
@@ -750,6 +750,7 @@ ElementTree Objects
       *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 or Unicode (default is ``None``).
+      *default_namespace* sets the default XML namespace (for "xmlns").
       *method* is either ``"xml"``, ``"html"`` or ``"text"`` (default is
       ``"xml"``).
 
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 9553c51f6c5..e8e309c3a04 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -789,11 +789,12 @@ class ElementTree:
     # @param **options Options, given as keyword arguments.
     # @keyparam encoding Optional output encoding (default is US-ASCII).
     #     Use "unicode" to return a Unicode string.
-    # @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 or Unicode.  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,
               encoding=None,