diff --git a/wp-includes/post-template.php b/wp-includes/post-template.php
index 2f84b72774..27fe5611ca 100644
--- a/wp-includes/post-template.php
+++ b/wp-includes/post-template.php
@@ -1305,7 +1305,7 @@ class Walker_Page extends Walker {
 
 		if ( ! empty( $current_page ) ) {
 			$_current_page = get_post( $current_page );
-			if ( in_array( $page->ID, $_current_page->ancestors ) ) {
+			if ( $_current_page && in_array( $page->ID, $_current_page->ancestors ) ) {
 				$css_class[] = 'current_page_ancestor';
 			}
 			if ( $page->ID == $current_page ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7cde277d51..2aa56b53a0 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.1-alpha-30156';
+$wp_version = '4.1-alpha-30157';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.