diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 98f63fb83f87a0..880f252f84aa0b 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -1141,8 +1141,7 @@ always available.
 .. data:: platlibdir
 
    Name of the platform-specific library directory. It is used to build the
-   path of platform-specific dynamic libraries and the path of the standard
-   library.
+   path of standard library and the paths of installed extension modules.
 
    It is equal to ``"lib"`` on most platforms. On Fedora and SuSE, it is equal
    to ``"lib64"`` on 64-bit platforms which gives the following ``sys.path``
@@ -1153,8 +1152,10 @@ always available.
    * ``/usr/lib64/pythonX.Y/lib-dynload/``:
      C extension modules of the standard library (like the :mod:`errno` module,
      the exact filename is platform specific)
-   * ``/usr/lib/pythonX.Y/site-packages`` (always use ``lib``, not
+   * ``/usr/lib/pythonX.Y/site-packages/`` (always use ``lib``, not
      :data:`sys.platlibdir`): Third-party modules
+   * ``/usr/lib64/pythonX.Y/site-packages/``:
+     C extension modules of third-party packages
 
    .. versionadded:: 3.9
 
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index d72fea2c67968c..04cc76ec6a0667 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -552,10 +552,9 @@ sys
 ---
 
 Add a new :attr:`sys.platlibdir` attribute: name of the platform-specific
-library directory. It is used to build the path of platform-specific dynamic
-libraries and the path of the standard library. It is equal to ``"lib"`` on
-most platforms.  On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit
-platforms.
+library directory. It is used to build the path of standard library and the
+paths of installed extension modules. It is equal to ``"lib"`` on most
+platforms.  On Fedora and SuSE, it is equal to ``"lib64"`` on 64-bit platforms.
 (Contributed by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner in :issue:`1294959`.)
 
 Previously, :attr:`sys.stderr` was block-buffered when non-interactive. Now
diff --git a/Misc/NEWS.d/3.9.0a5.rst b/Misc/NEWS.d/3.9.0a5.rst
index 7e2eaa3a100c26..01cbd4423426ed 100644
--- a/Misc/NEWS.d/3.9.0a5.rst
+++ b/Misc/NEWS.d/3.9.0a5.rst
@@ -990,7 +990,7 @@ modules are built.
 Add ``--with-platlibdir`` option to the configure script: name of the
 platform-specific library directory, stored in the new
 :attr:`sys.platlibdir` attribute. It is used to build the path of
-platform-specific dynamic libraries and the path of the standard library. It
+platform-specific extension modules and the path of the standard library. It
 is equal to ``"lib"`` on most platforms. On Fedora and SuSE, it is equal to
 ``"lib64"`` on 64-bit platforms. Patch by Jan Matějek, Matěj Cepl,
 Charalampos Stratakis and Victor Stinner.