diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 46d303a..3f30127 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -1966,6 +1966,11 @@
       if __name__ == '__main__':
           unittest.main(verbosity=2)
 
+   The *defaultTest* argument is either the name of a single test or an
+   iterable of test names to run if no test names are specified via *argv*.  If
+   not specified or ``None`` and no test names are provided via *argv*, all
+   tests found in *module* are run.
+
    The *argv* argument can be a list of options passed to the program, with the
    first element being the program name.  If not specified or ``None``,
    the values of :data:`sys.argv` are used.