Error with pre_get_posts

function search_filter($query) {

	if (is_search()) {
		$query->set('post_parent__not_in', array(560));
		$query->set('posts_per_page', -1);
	}

	return $query;
}

add_action( 'pre_get_posts', 'search_filter' );

File function.php

Nothing happens, the changes are not present. What could be the problem?
If you insert exit() in check it works.