Images in CPT feed

Hey Guys

I hope you are all well, I am working on trying to show images in my rss feed for a custom post type, I have this working for normal posts but cant seem to get it working for the CPT, I think the problem I have is that CPT does not use a Featured Image like normal posts hence my dilemma, the them instead has an image gallery.

Here is the code I am trying to get to work, as you can see my CPT is called ad_listing as the theme is based on classified ads, any suggestions would really help me out.

Thanks and regards

Wes Dunn

function insertThumbnailRSS($content) {
global $post;
if ( has_post_thumbnail( $post->ID ) && $post->post_type == ‘ad_listing’ ){
$content = ” . get_the_post_thumbnail( $post->ID, ‘thumbnail’ ) . ” . $content;
}
return $content;
}

add_filter(‘the_excerpt_rss’, ‘insertThumbnailRSS’);
add_filter(‘the_content_feed’, ‘insertThumbnailRSS’);