Change “You are now logged out” text

I want to wrap <strong></strong> around the words “logged out”:

add_filter( 'gettext', 'wpse17709_gettext', 10, 2 );
function wpse17709_gettext( $custom_translation, $login_texts ) {

    // Messages
    if ( 'You are now logged out.' == $login_texts ) { return ''; } // Log out message

    return $translation
}

…however adding HTML elements to the text string breaks my page.

How can I add <strong></strong> to this message text? Is there a means other than gettext?

This allows for the message to be overwritten specifically for the loggedout message while leaving all other messages alone. Here is more documentation on the filter.

add_filter( 'wp_login_errors', 'my_logout_message' );

function my_logout_message( $errors ){

    if ( isset( $errors->errors['loggedout'] ) ){
        $errors->errors['loggedout'][0] = 'This is the <strong style="color:red;">logged out</strong> message.';
    }

    return $errors;
}