tribe_rsvp_email_headers doesn’t work?

Anyone have any ideas why this simple (test) snippet to add a bcc to the rsvp email doesn’t work? I’ve tried many different things, but it seems the filter ‘tribe_rsvp_email_headers’ has no effect. I am using the free version of Event Tickets, is that filter only available for the pro version?

add_filter( ‘tribe_rsvp_email_headers’, ‘tribe_modify_the_rsvp_email_headers’, 10, 3 );
function tribe_modify_the_rsvp_email_headers( $headers ) {
$headers = array( ‘Content-type: text/html’, ‘Bcc: Test [email protected]‘ );
return $headers;
}

Thanks for any ideas.