Compatibility Mode

I see where there is a message about adding this to the functions.php file but there is more than one of them. No one says which functions.php to add this code to

#—————————————————————–
# Fix Shortcodes Ultimate Compatibility Mode
#—————————————————————–
update_option(‘su_compatibility_mode_prefix’, ‘gn_’);

I also don’t have on the settings page Compatibility Mode.

http://wordpress.org/plugins/shortcodes-ultimate/