Problem with multiple optional contexts

I am not sure if this is a Panels or CTools problem, but I have a Panels/CTools content type configured like this:

function ding_campaign_relevant_content_type_content_types() {
  $types = array(
    'relevant_campaigns' => array(
      'title' => t('Relevant campaigns'),
      'category' => t('Miscellaneous'),
      'required context' => array(
        new ctools_context_optional(t('Page node'), 'node'), 
        new ctools_context_optional(t('Related library'), 'node'),
      ),
    ),
  );
  return $types;
}

This works beautifully as long as the content type receives one or both of these contexts – but if it receives neither, the content type is not rendered (makes sense, since the context is supposed to be required).

Now, according to panels/docs/sample_plugin_ct.inc, line 289-294, there is a similar property called 'optional context', but if I try to use that instead of 'required context', the contexts stop working at all, not being passed to the rendering function and not appearing in the panels admin (If you have multiple nodes and/or context that receive them, selectors appear to let you pick which one goes where).