Cannot redeclare class Helper

Hi! Thanks for the plugin, but I have this issue:

If user click “subscribe without commenting” he gets this error:

Fatal error: Cannot redeclare class Helper in /wp-content/plugins/subscribe-to-comments-reloaded/classes/helper.class.php on line 15

Example url: http://magazeta.com/2014/01/qiujin/
(find in text “Вы можете подписаться без” and click to “подписаться” link to get the error)

Any idea how to fix it? Thanks!

http://wordpress.org/plugins/subscribe-to-comments-reloaded/