wp_update_post inserts empty title and content

$my_post = array(
	'ID'  => $postID,
	 'post_title'    => $post_title, // doesnt work, inserts empty value
	'post_content'  => "works"
);

wp_update_post( $my_post, true );

What am I doing wrong? And yes, there’s something in $post_title.