"The e-mail address you supplied is not valid" error on block validation

I've got a Simplenews block set up to allow anonymous users to submit their emails to join the newseletter. However, the validation always responds with the above error, even if the email address is valid. What I found is that the problem is tied to the following code:

<?php
/*
 * FAPI BLOCK subscription form_validate.
 */
function simplenews_block_form_validate($form, &$form_state) {
  if (!valid_email_address($form_state['values']['mail'])) {
    form_set_error('mail', t("The e-mail address you supplied is not valid."));
  }
}
?>

The issue is that $form_state['values']['mail'] always holds the value "Email Address", rather than the submitted value itself. What it should reference is $form_state['input']['mail'] and for uniformity with the other validation routines executed later in the file, I rewrote it like so:

<?php
function simplenews_block_form_validate($form, &$form_state) {
	$valid_email = valid_email_address($form_state['input']['mail']);
	if (!$valid_email) {
    form_set_error('mail', t("The e-mail address you supplied is not valid."));
  }
}
?>