untranslatable button caption

hey there,

the Quiz module features multi-step forms (quizzes) in which every page has a question. there's a button at the bottom which says either "Next" or "Finish", wether the user is on the last page or not.

now those buttons' captions are wrapped in t() but they can't be translated.

here's the relevant code:

  // Add navigation at the bottom:
  $form['navigation']['submit'] = array(
    '#type' => 'submit',
    '#value' => $is_last ? t('Finish') : t('Next'),
  );

I visited admin/config/regional/translate/i18n_string and refreshed strings for all text groups - multiple times. no joy.

if you need more info, please let me know. thanks!

cheers,
Luciano