Crop position does not work with "add_image_size"

Has anyone managed to get “crop position” to work with “add_image_size”? I would like to crop an image from the top, but it always crops from the center (default).

I have followed the example in the Codex: https://codex.www.ads-software.com/Function_Reference/add_image_size#Crop_Mode

Code in functions.php:

if ( function_exists( 'add_theme_support' ) ) {
  add_theme_support( 'post-thumbnails' );
}
add_image_size( 'portrait', 200, 300, true );
add_image_size( 'portrait-square', 250, 250, array( 'center', 'top' ));

Code in page.php:
<? the_post_thumbnail('portrait-square'); ?>

I’ve tried this on two different wordpress installs (both local and ftp), and have regenerated the thumbnails.