Index: wp-admin/includes/post.php
===================================================================
--- wp-admin/includes/post.php	(revision 21533)
+++ wp-admin/includes/post.php	(working copy)
@@ -488,7 +488,7 @@
  * @param string $title Post title
  * @param string $content Optional post content
  * @param string $date Optional post date
- * @return int Post ID if post exists, 0 otherwise.
+ * @return int Post ID if post exists, null otherwise.
  */
 function post_exists($title, $content = '', $date = '') {
 	global $wpdb;
@@ -518,7 +518,7 @@
 	if ( !empty ( $args ) )
 		return $wpdb->get_var( $wpdb->prepare($query, $args) );
 
-	return 0;
+	return null;
 }
 
 /**