Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 18753)
+++ wp-includes/post-template.php	(working copy)
@@ -1234,17 +1234,21 @@
  * @uses $wp_query
  *
  * @param string $template The specific template name if specific matching is required.
+ * @param string $id The ID of the page you'd like to check. Leave blank to use current page.
  * @return bool False on failure, true if success.
  */
-function is_page_template($template = '') {
-	if (!is_page()) {
+function is_page_template($template = '', $id = '') {
+	if ( !is_page() ) {
 		return false;
 	}
 
-	global $wp_query;
-
-	$page = $wp_query->get_queried_object();
-	$custom_fields = get_post_custom_values('_wp_page_template',$page->ID);
+	if( empty( $id ) )  {
+		global $wp_query;
+		$page = $wp_query->get_queried_object();
+		$id = $page->ID;
+	}
+	
+	$custom_fields = get_post_custom_values( '_wp_page_template', $id );
 	$page_template = $custom_fields[0];
 
 	// We have no argument passed so just see if a page_template has been specified