Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 21568)
+++ wp-includes/post.php	(working copy)
@@ -381,6 +381,10 @@
 	$null = null;
 
 	if ( empty( $post ) && isset( $GLOBALS['post'] ) ) {
+		if ( !is_a( $GLOBALS['post'], 'WP_Post' ) ) {
+			return get_post( $GLOBALS['post'], $output, $filter );
+		}
+
 		$_post = & $GLOBALS['post'];
 	} elseif ( is_a( $post, 'WP_Post' ) ) {
 		$_post = $post;