Documented QueueListener change.
diff --git a/Doc/library/logging.handlers.rst b/Doc/library/logging.handlers.rst
index eda9302..9346e99 100644
--- a/Doc/library/logging.handlers.rst
+++ b/Doc/library/logging.handlers.rst
@@ -838,6 +838,15 @@
       Note that if you don't call this before your application exits, there
       may be some records still left on the queue, which won't be processed.
 
+   .. method:: enqueue_sentinel()
+
+      Writes a sentinel to the queue to tell the listener to quit. This
+      implementation uses ``put_nowait()``.  You may want to override this
+      method if you want to use timeouts or work with custom queue
+      implementations.
+
+      .. versionadded:: 3.3
+
 
 .. seealso::