Shortcode shows solely default attribute values

For some causes each shortcode, that I attempt to add to features.php, shows solely default attribute worth and ignores what I specify in a put up. E.g.:

perform my_shortcode( $atts ) {
    extract( shortcode_atts(
        array(
            'id' => '18',
        ), $atts )
    );
    return $id;
}
add_shortcode( 'sc', 'my_shortcode' );

So I exploit shortcode [sc id="81"] and count on echoing 81 however I get 18. BTW I exploit little one theme, and newest model of wordpress. I am actually caught. Thanks for any assist.