diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 7f22a5d1852a89..d6b892a7ed957d 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -791,9 +791,10 @@ Instances of the :class:`Popen` class have the following methods:
 
    .. note::
 
-      The function is implemented using a busy loop (non-blocking call and
-      short sleeps). Use the :mod:`asyncio` module for an asynchronous wait:
-      see :class:`asyncio.create_subprocess_exec`.
+      When the ``timeout`` parameter is not ``None``, then (on POSIX) the
+      function is implemented using a busy loop (non-blocking call and short
+      sleeps). Use the :mod:`asyncio` module for an asynchronous wait: see
+      :class:`asyncio.create_subprocess_exec`.
 
    .. versionchanged:: 3.3
       *timeout* was added.