diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 58f057a..4b2f8ec 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -279,8 +279,11 @@
 
    Return the value of the environment variable *key* if it exists, or
    *default* if it doesn't. *key*, *default* and the result are bytes.
+
    Availability: most flavors of Unix.
 
+   .. versionadded:: 3.2
+
 
 .. function:: putenv(key, value)