Show post thumbnails in RSS Feed

function snipjar_feed_post_thumbnail($content) {
global $post;
if(has_post_thumbnail($post->ID)) {
$content = '' . $content;
}
return $content;
}
add_filter('the_excerpt_rss', 'snipjar_feed_post_thumbnail');
add_filter('the_content_feed', 'snipjar_feed_post_thumbnail');