‘Show on screen’ for custom taxonomies does not save

I have noticed that on the admin screen for viewing custom taxonomies that WordPress does not seem to save the ‘show on screen’ screen option. Upon changing it and clicking apply, the screen reloads and the value is back to 20.

This does not occur with the WordPress built-in categories and tags. Only custom taxonomies. The other screen options (which columns to show/hide) behave as expected.

Have I unearthed a bug, or I am expected to implement this option (or have I neglected an option when registering the taxonomy) ?

EDIT

I have made the a test plug-in, here is the code. I have tested this on WP3.3, TwentyEleven theme.

<?php
/*
Plugin Name: Test Plugin
Version: 1
*/

add_action( 'init', 'create_Test_taxonomies', 0 );
function create_Test_taxonomies() {
  $category_labels = array(
    'name' => _x( 'Test Categories', 'taxonomy general name' ),
    'singular_name' => _x( 'Category', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Categories' ),
    'all_items' => __( 'All Categories' ),
    'parent_item' => __( 'Parent Category' ),
    'parent_item_colon' => __( 'Parent Category:' ),
    'edit_item' => __( 'Edit Category' ), 
    'update_item' => __( 'Update Category' ),
    'add_new_item' => __( 'Add New Category' ),
    'new_item_name' => __( 'New Category Name' ),
    'not_found' =>  __('No categories found'),
    'menu_name' => __( 'Test Categories' ),
  );    

register_taxonomy('test-cat',array('post'), array(
    'hierarchical' => true,
    'labels' => $category_labels,
    'show_ui' => true,
    'query_var' => true,
    'public'=> true,
  ));
}