issue with parabola 1.3.1

Hi,

i made a little change on the function file to add post thumbnail to my rss using this code :
function rss_post_thumbnail($content) {
global $post;
if(has_post_thumbnail($post->ID)) {
$content = ‘<p>’ . get_the_post_thumbnail($post->ID,array(150,150)) .'</p>’ . get_the_content();
}
return $content;
}
add_filter(‘the_excerpt_rss’, ‘rss_post_thumbnail’);
add_filter(‘the_content_feed’, ‘rss_post_thumbnail’);
This was wroking fine, but when i updated to parabola 1.3.1, i had a small problem : my rss feed was displaying the full post (and not the excerpt as set). So i deactivated this extra code, and RSS feed came back to normal. But i really want to keep this change on my feed. Do you have any idea where it can comme from?
I will test also on 1.3.2..

Thanks guys!