Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 21259)
+++ wp-includes/post-template.php	(working copy)
@@ -319,7 +319,8 @@
 		return $classes;
 
 	$classes[] = 'post-' . $post->ID;
-	$classes[] = $post->post_type;
+	if ( ! is_admin() )
+		$classes[] = $post->post_type;
 	$classes[] = 'type-' . $post->post_type;
 	$classes[] = 'status-' . $post->post_status;