#4446: document "platforms" argument for setup().
diff --git a/Doc/distutils/setupscript.rst b/Doc/distutils/setupscript.rst
index 1e540ed..7971878 100644
--- a/Doc/distutils/setupscript.rst
+++ b/Doc/distutils/setupscript.rst
@@ -563,6 +563,8 @@
+----------------------+---------------------------+-----------------+--------+
| ``classifiers`` | a list of classifiers | list of strings | \(4) |
+----------------------+---------------------------+-----------------+--------+
+| ``platforms`` | a list of platforms | list of strings | |
++----------------------+---------------------------+-----------------+--------+
Notes: