diff --git a/tests/phpunit/tests/query/thePost.php b/tests/phpunit/tests/query/thePost.php
index 6032a01dbeb1b..70e96541838df 100644
--- a/tests/phpunit/tests/query/thePost.php
+++ b/tests/phpunit/tests/query/thePost.php
@@ -110,7 +110,7 @@ function ( $fields, $query ) {
 				'fields'    => 'custom',
 				'post_type' => 'page',
 				'post__in'  => self::$page_child_ids,
-				'orderby'   => 'id',
+				'orderby'   => 'ID',
 				'order'     => 'ASC',
 			)
 		);