diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 2b3821bb3ee..9c983a19a51 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -217,8 +217,7 @@ process and user.
 .. function:: getenv(key, default=None)
 
    Return the value of the environment variable *key* if it exists, or
-   *default* if it doesn't. Only *key* needs to be a string as it is used to
-   lookup the value in os.environ.
+   *default* if it doesn't. *key* must be a string.
 
    On Unix, keys and values are decoded with :func:`sys.getfilesystemencoding`
    and ``'surrogateescape'`` error handler. Use :func:`os.getenvb` if you