Post Format aside, remove link from title in Thematic

gistfile1.php

function childtheme_custom_postheader($postheader) {
    if ( has_post_format( 'aside' ) && ! is_single()) {
        $postheader = '<h2 class="entry-title">';
        $postheader .= get_the_title();
        $postheader .= '</h2>';
    }
    return $postheader;
}
add_filter ('thematic_postheader', 'childtheme_custom_postheader');