Fieldtype save() method not being called in SAEF

I’m developing a custom fieldtype. It is an array of input data, so in my save method I serialize the data.

function save($data)
{
        return ($data) ? base64_encode(serialize($data)) : '';
}

That works great from within the CP. But if I try using a SAEF, I get a MySQL error:

INSERT INTO exp_channel_data (`entry_id`, `channel_id`, `site_id`, `field_id_3`, `field_id_4`, `field_id_5`, `field_id_6`, `field_id_13`, `field_id_1`, `field_ft_6`) VALUES (27, '1', '1', '', '', '', 0, 0, Array, 'none')

It looks like my POSTed array is never getting serialized. I traced through the code, and found that when $this->EE->api_channel_entries->submit_new_entry() is called from within channel_standalone->insert_new_entry(), that after the api_channel_fields class is instantiated, it’s settings array is empty: $this->EE->api_channel_fields->settings (around line 1563 in Api_channel_entries), and so the save method of the fieldtype never gets called.

Any work arounds? Am I being dumb in some way? I’m using v2.0.2pb01. Thanks.