diff --git a/wp-includes/rewrite.php b/wp-includes/rewrite.php
index a03754f272..2666ff6f97 100644
--- a/wp-includes/rewrite.php
+++ b/wp-includes/rewrite.php
@@ -273,7 +273,10 @@ function add_feed( $feedname, $function ) {
  */
 function flush_rewrite_rules( $hard = true ) {
 	global $wp_rewrite;
-	$wp_rewrite->flush_rules( $hard );
+
+	if ( is_callable( array( $wp_rewrite, 'flush_rules' ) ) ) {
+		$wp_rewrite->flush_rules( $hard );
+	}
 }
 
 /**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 3d09776eb0..acabe2ec7d 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45698';
+$wp_version = '5.3-alpha-45699';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.