diff --git a/wp-includes/post-thumbnail-template.php b/wp-includes/post-thumbnail-template.php
index ab8941f70..16952d03c 100644
--- a/wp-includes/post-thumbnail-template.php
+++ b/wp-includes/post-thumbnail-template.php
@@ -50,9 +50,12 @@ function the_post_thumbnail( $size = 'post-thumbnail', $attr = '' ) {
  * Update cache for thumbnails in the current loop
  *
  * @since 3.2
+ *
+ * @param object $wp_query Optional. A WP_Query instance. Defaults to the $wp_query global.
  */
-function update_post_thumbnail_cache() {
-	global $wp_query;
+function update_post_thumbnail_cache( $wp_query = null ) {
+	if ( ! $wp_query )
+		$wp_query = $GLOBALS['wp_query'];
 
 	if ( $wp_query->thumbnails_cached )
 		return;