diff -r a366d3684bc0 Doc/distutils/apiref.rst
--- a/Doc/distutils/apiref.rst	Sun Oct 09 17:29:14 2011 +0100
+++ b/Doc/distutils/apiref.rst	Tue Oct 11 18:14:16 2011 -0700
@@ -162,6 +162,10 @@
    The Extension class describes a single C or C++extension module in a setup
    script. It accepts the following keyword arguments in its constructor:
 
+   When declaring an extension that's part of a package (i.e. ``package.ext``),
+   a directory with an :file:`__init__.py` file has be to be present, just like
+   any other package.
+
    +------------------------+--------------------------------+---------------------------+
    | argument name          | value                          | type                      |
    +========================+================================+===========================+
diff -r a366d3684bc0 Doc/distutils/setupscript.rst
--- a/Doc/distutils/setupscript.rst	Sun Oct 09 17:29:14 2011 +0100
+++ b/Doc/distutils/setupscript.rst	Tue Oct 11 18:14:16 2011 -0700
@@ -228,6 +228,9 @@
 Visual C++. These will be compiled to binary resource (:file:`.res`) files and
 linked into the executable.
 
+When declaring an extension that's part of a package (i.e. ``package.ext``), 
+a directory with an :file:`__init__.py` file has to be present, just like 
+any other package.
 
 Preprocessor options
 --------------------