pm-uninstall warnings on Drupal 6

$ drush pm-uninstall -y migrate_example
WD php: Notice: Undefined property: stdClass::$required_by in drush_pm_uninstall() (line 1028 of                        [error]
/Users/mikeryan/bin/drush/commands/pm/pm.drush.inc).
WD php: Warning: array_keys() expects parameter 1 to be array, null given in drush_pm_uninstall() (line 1028 of         [error]
/Users/mikeryan/bin/drush/commands/pm/pm.drush.inc).
WD php: Warning: Invalid argument supplied for foreach() in drush_pm_uninstall() (line 1028 of                          [error]
/Users/mikeryan/bin/drush/commands/pm/pm.drush.inc).
The following modules will be uninstalled: migrate_example
Do you really want to continue? (y/n): y
migrate_example was successfully uninstalled.                                                                           [ok]
array_keys() expects parameter 1 to be array, null given in drush_pm_uninstall() (line 1028 of                          [warning]
/Users/mikeryan/bin/drush/commands/pm/pm.drush.inc).
Invalid argument supplied for foreach() in drush_pm_uninstall() (line 1028 of                                           [warning]
/Users/mikeryan/bin/drush/commands/pm/pm.drush.inc).

drush_pm_uninstall() is checking the module's required_by array to see if anything else needs to be disabled - unfortunately, required_by is a D7ism.