Add Featured Images to RSS Feed

<?php
add_filter( 'the_excerpt_rss',  'scseed_featured_image_in_rss' );
add_filter( 'the_content_feed', 'scseed_featured_image_in_rss' );
if ( ! function_exists( 'scseed_featured_image_in_rss' ) ) {
    function scseed_featured_image_in_rss( $content ) {
        global $post;
        if ( has_post_thumbnail( $post->ID ) ) {
            $thumb   = get_the_post_thumbnail( $post->ID, 'full' );
            $content = $thumb . $content;
        }
        return $content;
    }
}