Untranslated CAPTCHA description in comment submission form

I'm using v.3.1 in my personal site. I've also updated the Greek translation according to the latest stable version (3.1). Using Greek as the default language in my site, in the comment submission forms, I notice that the description

This question is for testing whether you are a human visitor and to prevent automated spam submissions.

remains untranslated, although I did translated the corresponding msgid string. The other messages appear in Greek fine. I noticed these two lines in captcha.module (lines 145-148, function _captcha_get_description()):

    $description = variable_get("captcha_description_$lang_code", t('This question is for testing whether you are a human visitor and to prevent automated spam submissions.'));
  }
  else {
    $description = variable_get('captcha_description', t('This question is for testing whether you are a human visitor and to prevent automated spam submissions.'));

Insights?

Merry Christmas everyone! :-)