Invalid argument supplied for foreach() in pay_form->form_validate()

Not sure if related to #1130314: Invalid argument, that's D6 and this is D7.

I'm trying pay.module along with donate.module on D7. Trying to get simple paypal to work.

When I submit a donate form, I get
Warning: Invalid argument supplied for foreach() in pay_form->form_validate() (line 369 of /srv/work.electricgroups.com/dave/fridge/profiles/custom/modules/pay/includes/handlers/pay_form.inc).

The line with the warning is

    // If there is no total value per payment method, set the global total.                                         
    foreach ($values['pay_method']['selected'] as $pmid => $status) {                                               

And the reason is that $values['pay_method']['selected'] is "2", not an array.

I can't tell whether this validation function is broken or the form elements are broken. I'm not sure why it tries to support multiple payment methods in a single submit.