Multisite Error

Hi

I am using your plugin on a Multisite install but when I enable the plugin I get the following error:

Fatal error: Uncaught Error: Call to undefined function wp_get_current_user() in /home/XXXXX/public_html/wp-includes/capabilities.php:652 Stack trace: #0 /home/XXXXX/public_html/wp-content/plugins/contributor-notifications/contributor-notifications.php(23): current_user_can(‘edit_others_pos…’) #1 /home/XXXXX/public_html/wp-settings.php(360): include_once(‘/home/XXXXX…’) #2 /home/XXXXX/public_html/wp-config.php(102): require_once(‘/home/XXXXX…’) #3 /home/XXXXX/public_html/wp-load.php(37): require_once(‘/home/XXXXX…’) #4 /home/XXXXX/public_html/wp-admin/admin.php(34): require_once(‘/home/XXXXX…’) #5 /home/XXXXX/public_html/wp-admin/plugins.php(10): require_once(‘/home/XXXXX…’) #6 {main} thrown in /home/XXXXX/public_html/wp-includes/capabilities.php on line 652

I am using the latest version of WP.