Index: wp-includes/link-template.php
===================================================================
--- wp-includes/link-template.php	(revision 18660)
+++ wp-includes/link-template.php	(working copy)
@@ -2405,7 +2405,7 @@
 	$shortlink = '';
 
 	// Return p= link for posts.
-	if ( !empty($post_id) && '' != get_option('permalink_structure') ) {
+	if ( !empty($post_id) ) {
 		$post = get_post($post_id);
 		if ( isset($post->post_type) && 'post' == $post->post_type )
 			$shortlink = home_url('?p=' . $post->ID);