I guess you don’t use it at all, so why don’t you just remove the filter?
remove_filter('the_content', 'wpautop');
remove_filter('the_excerpt', 'wpautop');
I’ve tested it a few minutes ago (on WP 4.3) and it works.
p.s. I just saw that you use the same function. Sorry for that. What version are you using? This disables the wpautop on 4.3.