diff --git a/doc/libalsaaudio.rst b/doc/libalsaaudio.rst
index e7dacb9..dbfdfb5 100644
--- a/doc/libalsaaudio.rst
+++ b/doc/libalsaaudio.rst
@@ -807,6 +807,9 @@ Play back the recording with::
 
    $ python playbacktest.py <filename>
 
+playbacktest.py accepts the commandline option
+ *-d <device>*.
+
 mixertest.py
 ~~~~~~~~~~~~