diff --git a/src/wp-includes/sitemaps/class-wp-sitemaps-provider.php b/src/wp-includes/sitemaps/class-wp-sitemaps-provider.php
index 3440f62b34a4c..e77681d7215d3 100644
--- a/src/wp-includes/sitemaps/class-wp-sitemaps-provider.php
+++ b/src/wp-includes/sitemaps/class-wp-sitemaps-provider.php
@@ -160,7 +160,7 @@ public function get_sitemap_url( $name, $page ) {
 		);
 
 		if ( ! $wp_rewrite->using_permalinks() ) {
-			$basename = '/?' . http_build_query( $params, null, '&' );
+			$basename = '/?' . http_build_query( $params, '', '&' );
 		}
 
 		return home_url( $basename );