Does not work with WP 4.1!

Error on plugin activation: Warning: require_once(): Unable to access class.ez_functions.php in (…)/wp-content/plugins/ez-form-calculator/class.ezfc_backend.php on line 3 Warning: require_once(class.ez_functions.php): failed to open stream: No such file or directory in (…)/wp-content/plugins/ez-form-calculator/class.ezfc_backend.php on line 3 Fatal error: require_once(): Failed opening required ‘class.ez_functions.php’ (include_path=’.:’) in (…)/wp-content/plugins/ez-form-calculator/class.ezfc_backend.php on line 3