diff --git a/wp-includes/rest-api.php b/wp-includes/rest-api.php
index 7480fd5c64..675c545ce1 100644
--- a/wp-includes/rest-api.php
+++ b/wp-includes/rest-api.php
@@ -2818,6 +2818,11 @@ function rest_preload_api_request( $memo, $path ) {
 		}
 	}
 
+	$path = untrailingslashit( $path );
+	if ( empty( $path ) ) {
+		$path = '/';
+	}
+
 	$path_parts = parse_url( $path );
 	if ( false === $path_parts ) {
 		return $memo;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 068dffae2e..4e38a362ca 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51647';
+$wp_version = '5.9-alpha-51648';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.