WordPress 2.5 wp_list_pages Errors

wp_list_pages in 2.3.3:

function wp_list_pages($args = '') {
	$defaults = array(
		'depth' => 0, 'show_date' => '',
		'date_format' => get_option('date_format'),
		'child_of' => 0, 'exclude' => '',
		'title_li' => __('Pages'), 'echo' => 1,
		'authors' => '', 'sort_column' => 'menu_order, post_title'
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	$output = '';
	$current_page = 0;

	// sanitize, mostly to keep spaces out
	$r['exclude'] = preg_replace('[^0-9,]', '', $r['exclude']);

	// Allow plugins to filter an array of excluded pages
	$r['exclude'] = implode(',', apply_filters('wp_list_pages_excludes', explode(',', $r['exclude'])));

	// Query pages.
	$pages = get_pages($r);

	if ( !empty($pages) ) {
		if ( $r['title_li'] )
			$output .= '<li class="pagenav">' . $r['title_li'] . '<ul>';

		global $wp_query;
		if ( is_page() )
			$current_page = $wp_query->get_queried_object_id();
		$output .= walk_page_tree($pages, $r['depth'], $current_page, $r);

		if ( $r['title_li'] )
			$output .= '</ul></li>';
	}

	$output = apply_filters('wp_list_pages', $output);

	if ( $r['echo'] )
		echo $output;
	else
		return $output;
}

wp_list_pages in 2.5:

function wp_list_pages($args = '') {
	$defaults = array(
		'depth' => 0, 'show_date' => '',
		'date_format' => get_option('date_format'),
		'child_of' => 0, 'exclude' => '',
		'title_li' => __('Pages'), 'echo' => 1,
		'authors' => '', 'sort_column' => 'menu_order, post_title'
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	$output = '';
	$current_page = 0;

	// sanitize, mostly to keep spaces out
	$r['exclude'] = preg_replace('[^0-9,]', '', $r['exclude']);

	// Allow plugins to filter an array of excluded pages
	$r['exclude'] = implode(',', apply_filters('wp_list_pages_excludes', explode(',', $r['exclude'])));

	// Query pages.
	$r['hierarchical'] = 0;
	$pages = get_pages($r);

	if ( !empty($pages) ) {
		if ( $r['title_li'] )
			$output .= '<li class="pagenav">' . $r['title_li'] . '<ul>';

		global $wp_query;
		if ( is_page() || $wp_query->is_posts_page )
			$current_page = $wp_query->get_queried_object_id();
		$output .= walk_page_tree($pages, $r['depth'], $current_page, $r);

		if ( $r['title_li'] )
			$output .= '</ul></li>';
	}

	$output = apply_filters('wp_list_pages', $output);

	if ( $r['echo'] )
		echo $output;
	else
		return $output;
}

If I copy and paste the 2.3.3 code over the 2.5 code, the wp_list_pages function works properly.

The only difference between the 2 sets of codes are only:

//2.3.3
$pages = get_pages($r);

.......

global $wp_query;
		if ( is_page() )
			$current_page = $wp_query->get_queried_object_id();
		$output .= walk_page_tree($pages, $r['depth'], $current_page, $r);

//2.5
$r['hierarchical'] = 0;
$pages = get_pages($r);

..........

global $wp_query;
		if ( is_page() || $wp_query->is_posts_page )
			$current_page = $wp_query->get_queried_object_id();
		$output .= walk_page_tree($pages, $r['depth'], $current_page, $r);