undefined function drush_core_cache_clear() error when calling drush autoadmin-update-install

I'm a first time Auto Admin user.

After creating my first forms I'm trying to update some of my tables definitions. When I call drush autoadmin-update-install dv dv_database dv_variable dv_option I get the expected output, i.e., the updated install file but I also get the following error:

Fatal error: Call to undefined function drush_core_cache_clear() in /var/www/localhost/drupal6/sites/all/modules/autoadmin/drush/autoadmin.drush.update.install.inc on line 36

Call Stack:
0.0006 193736 1. {main}() /usr/local/drush/drush.php:0
0.0149 2227960 2. drush_main() /usr/local/drush/drush.php:40
1.3646 25083400 3. drush_dispatch() /usr/local/drush/drush.php:90
1.3647 25087752 4. call_user_func_array() /usr/local/drush/includes/drush.inc:51
1.3647 25088576 5. autoadmin_drush_update_install() /usr/local/drush/includes/drush.inc:0