diff --git a/types/react-helmet/index.d.ts b/types/react-helmet/index.d.ts
index 57ac67f2a7..93b83075fe 100644
--- a/types/react-helmet/index.d.ts
+++ b/types/react-helmet/index.d.ts
@@ -7,9 +7,11 @@
 import * as React from "react";
 
 export interface HelmetProps {
+    async?: boolean;
     base?: any;
     bodyAttributes?: Object;
     defaultTitle?: string;
+    defer?: boolean;
     encodeSpecialCharacters?: boolean;
     htmlAttributes?: any;
     onChangeClientState?: (newState: any) => void;