Issue #18673: Add versionchanged to docs
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index cfcb062..82d05ed 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -924,6 +924,10 @@
    These constants are GNU extensions and not present if they are not defined by
    the C library.
 
+   .. versionchanged:: 3.4
+      Add :data:`O_TMPFILE` constant. It's only available on Linux Kernel 3.11
+      or newer.
+
 
 .. function:: openpty()