Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 22873)
+++ wp-includes/taxonomy.php	(working copy)
@@ -2238,6 +2238,8 @@
 				return new WP_Error( 'db_insert_error', __( 'Could not insert term relationship into the database' ), $wpdb->last_error );
 	}
 
+	wp_cache_delete( $object_id, $taxonomy . '_relationships' );
+
 	do_action('set_object_terms', $object_id, $terms, $tt_ids, $taxonomy, $append, $old_tt_ids);
 	return $tt_ids;
 }
Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 22873)
+++ wp-includes/post.php	(working copy)
@@ -3200,8 +3200,6 @@
 	if ( is_wp_error( $r ) )
 		return $r;
 
-	wp_cache_delete( $post_id, $taxonomy . '_relationships' );
-
 	return $r;
 }