Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 11140)
+++ wp-includes/post-template.php	(working copy)
@@ -311,7 +311,8 @@
 	$post = get_post($post_id);
 
 	$classes = array();
-
+	
+	$classes[] = 'post-' . $post->ID;
 	$classes[] = $post->post_type;
 
 	// sticky for Sticky Posts
@@ -323,16 +324,16 @@
 
 	// Categories
 	foreach ( (array) get_the_category($post->ID) as $cat ) {
-		if ( empty($cat->slug ) )
+		if ( empty($cat->cat_ID ) )
 			continue;
-		$classes[] = 'category-' . $cat->slug;
+		$classes[] = 'category-' . $cat->cat_ID;
 	}
 
 	// Tags
 	foreach ( (array) get_the_tags($post->ID) as $tag ) {
-		if ( empty($tag->slug ) )
+		if ( empty($tag->term_id ) )
 			continue;
-		$classes[] = 'tag-' . $tag->slug;
+		$classes[] = 'tag-' . $tag->term_id;
 	}
 
 	if ( !empty($class) ) {