Level setting on exported blocks not working

I have a block export looking like this:

  return array(
    'rvl_content-1' => array(
      'menu_name'   => 'main-menu',
      'parent_mlid' => 0,
      'title_link'  => 0,
      'admin_title' => 'Main menu, first level',
      'level'       => 1,
      'follow'      => 0,
      'depth'       => 1,
      'expanded'    => 0,
      'sort'        => 0,
    ),
    'rvl_content-2' => array(
      'menu_name'   => 'main-menu',
      'parent_mlid' => 0,
      'title_link'  => 0,
      'admin_title' => 'Main menu, second level',
      'level'       => 2,
      'follow'      => 0,
      'depth'       => 1,
      'expanded'    => 0,
      'sort'        => 0,
    ),
  );

As you can see, the level setting is set differently on each block, but when it's printed on the page, the blocks both display the first level menu items :(