it seems the platform arguments are now optional for pre_migrate & rollback hooks (?)

platform/migrate.provision.inc

@@ -30,7 +30,7 @@ function drush_provision_drupal_provision_migrate_validate($url = null, $platfor
 /**
  * Make a backup before making any changes, and add extract the file we are restoring from
  */
-function drush_provision_drupal_pre_provision_migrate($url, $platform) {
+function drush_provision_drupal_pre_provision_migrate($url, $platform = null) {
   /* Set offline mode to true and re-generate the settings.php. This will write a 
    * $conf['site_offline'] = 1; to the settings.php
    */
@@ -44,7 +44,7 @@ function drush_provision_drupal_pre_provision_migrate($url, $platform) {
  * Remove the extracted site directory
  * Restore the vhost conf per the original platform
  */
-function drush_provision_drupal_pre_provision_migrate_rollback($url, $platform) {
+function drush_provision_drupal_pre_provision_migrate_rollback($url, $platform = null) {
   // Set site_offline to false and regenerate the config 
   drush_log(dt("Bringing site out of maintenance"));
   drush_set_option('site_offline', 0);