Error during update

Received the following errors when updfating to version 4.0.1

An error of type E_ERROR was caused in line 874 of the file /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-page-cache.php. Error message: Uncaught Error: Class "WPO_File_System_Helper" not found in /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-page-cache.php:874
Stack trace: 0 /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-cache-config.php(169): WPO_Page_Cache->get_advanced_cache_version() 1 /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-cache-config.php(113): WPO_Cache_Config->write() 2 /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-page-cache.php(1021): WPO_Cache_Config->update() 3 /home/user/public_html/client1/wp-includes/class-wp-hook.php(324): WPO_Page_Cache->update_cache_config() 4 /home/user/public_html/client1/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 5 /home/user/public_html/client1/wp-includes/plugin.php(517): WP_Hook->do_action() 6 /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/file-based-page-cache-functions.php(795): do_action() 7 /home/user/public_html/client1/wp-content/plugins/wp-optimize/cache/class-wpo-cache-rules.php(399): wpo_cache_flush() 8 /home/user/public_html/client1/wp-includes/class-wp-hook.php(324): WPO_Cache_Rules->purge_cache() 9 /home/user/public_html/client1/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 10 /home/user/public_html/client1/wp-includes/plugin.php(517): WP_Hook->do_action() 11 /home/user/public_html/client1/wp-content/plugins/wp-optimize/wp-optimize.php(265): do_action() 12 /home/user/public_html/client1/wp-includes/class-wp-hook.php(324): WP_Optimize->detect_active_plugins_and_themes_updates() 13 /home/user/public_html/client1/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 14 /home/user/public_html/client1/wp-includes/plugin.php(517): WP_Hook->do_action() 15 /home/user/public_html/client1/wp-admin/includes/class-plugin-upgrader.php(419): do_action() 16 /home/user/public_html/client1/wp-admin/includes/ajax-actions.php(4650): Plugin_Upgrader->bulk_upgrade() 17 /home/user/public_html/client1/wp-includes/class-wp-hook.php(324): wp_ajax_update_plugin() 18 /home/user/public_html/client1/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() 19 /home/user/public_html/client1/wp-includes/plugin.php(517): WP_Hook->do_action() 20 /home/user/public_html/client1/wp-admin/admin-ajax.php(192): do_action() 21 {main}