CRM_Core_BAO_Setting::setItem() followed by getItem() returns wrong result

Calling CRM_Core_BAO_Setting::setItem() to set something and then calling getItem right after seems to return the value from before you set it, not the new one. To reproduce, create a simple unit test where all within the same function you just do:

$mailingBackend = CRM_Core_BAO_Setting::getItem(CRM_Core_BAO_Setting::MAILING_PREFERENCES_NAME,
'mailing_backend'
);
$mailingBackend['outBound_option'] = 2;
CRM_Core_BAO_Setting::setItem($mailingBackend,
CRM_Core_BAO_Setting::MAILING_PREFERENCES_NAME,
'mailing_backend'
);

Then call getItem again and compare the results.