diff --git a/Doc/library/os.rst b/Doc/library/os.rst
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1183,13 +1183,14 @@
       single: UNC paths; and os.makedirs()
 
    Recursive directory creation function.  Like :func:`mkdir`, but makes all
-   intermediate-level directories needed to contain the leaf directory.  If
-   the target directory with the same mode as specified already exists,
-   raises an :exc:`OSError` exception if *exist_ok* is False, otherwise no
-   exception is raised.  If the directory cannot be created in other cases,
-   raises an :exc:`OSError` exception.  The default *mode* is ``0o777`` (octal).
-   On some systems, *mode* is ignored.  Where it is used, the current umask
-   value is first masked out.
+   intermediate-level directories needed to contain the leaf directory.  If the
+   target directory with the same mode as specified already exists, raises an
+   :exc:`OSError` exception unless *exist_ok* is True.  If the target directory
+   exists with a mode that differs from the one supplied, an :exc:`OSError` is
+   raised no matter what *exist_ok* is set to.  Also, if the directory cannot
+   be created in other cases, an :exc:`OSError` exception is raised.  The
+   default *mode* is ``0o777`` (octal).  On some systems, *mode* is ignored.
+   Where it is used, the current umask value is first masked out.
 
    .. note::