diff --git a/types/express-mung/express-mung-tests.ts b/types/express-mung/express-mung-tests.ts
index 86106e2c59..77aebc6c05 100644
--- a/types/express-mung/express-mung-tests.ts
+++ b/types/express-mung/express-mung-tests.ts
@@ -1,7 +1,35 @@
 import { Request, Response } from "express";
 import * as mung from "express-mung";
 
-function redact(body: Object, req: Request, res: Response) {
-    return body;
+function redact(body: {}, req: Request, res: Response) {
+  return body;
 }
+
 mung.json(redact);
+mung.json(redact, { mungError: true });
+
+function redactAsync(body: {}, req: Request, res: Response) {
+  return Promise.resolve(body);
+}
+
+mung.jsonAsync(redactAsync);
+mung.jsonAsync(redactAsync, { mungError: true });
+
+function transformHeaders(req: Request, res: Response) {
+  return;
+}
+
+mung.headers(transformHeaders);
+
+function transformHeadersAsync(req: Request, res: Response) {
+  return Promise.resolve();
+}
+
+mung.headersAsync(transformHeadersAsync);
+
+function transformChunk(chunk: string | Buffer, encoding: string | null, req: Request, res: Response) {
+  return 'chunk';
+}
+
+mung.write(transformChunk);
+mung.write(transformChunk, { mungError: true });
diff --git a/types/express-mung/index.d.ts b/types/express-mung/index.d.ts
index e6de726cd8..1236dc86dc 100644
--- a/types/express-mung/index.d.ts
+++ b/types/express-mung/index.d.ts
@@ -1,4 +1,4 @@
-// Type definitions for express-mung 0.4.2
+// Type definitions for express-mung 0.5.1
 // Project: https://github.com/richardschneider/express-mung
 // Definitions by: Cyril Schumacher <https://github.com/cyrilschumacher>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
@@ -8,37 +8,50 @@
 /// <reference types="node"/>
 
 declare module "express-mung" {
-    import { Request, Response } from "express";
-    import * as http from "http";
+    import { Request, Response, RequestHandler } from "express";
 
     type Transform = (body: {}, request: Request, response: Response) => any;
-    type TransformHeader = (body: http.IncomingMessage, request: Request, response: Response) => any;
+    type TransformAsync = (body: {}, request: Request, response: Response) => PromiseLike<any>;
+    type TransformHeader = (request: Request, response: Response) => any;
+    type TransformHeaderAsync = (request: Request, response: Response) => PromiseLike<any>;
+    type TransformChunk = (chunk: string | Buffer, encoding: string | null, request: Request, response: Response) => string | Buffer;
+    type Options = { mungError: boolean };
 
     /**
      * Transform the JSON body of the response.
      * @param {Transform} fn A transformation function.
-     * @return {any} The body.
+     * @param {Options} [options] json options.
+     * @return {RequestHandler} Middleware to transform the body
      */
-    export function json(fn: Transform): any;
+    export function json(fn: Transform, options?: Options): RequestHandler;
 
     /**
-     * Transform the JSON body of the response.
-     * @param {Transform} fn A transformation function.
-     * @return {any} The body.
+     * Asynchronously transform the JSON body of the response.
+     * @param {TransformAsync} fn A transformation function.
+     * @param {Options} [options] jsonAsync options.
+     * @return {RequestHandler} Middleware to transform the body
      */
-    export function jsonAsync(fn: Transform): PromiseLike<any>;
+    export function jsonAsync(fn: TransformAsync, options?: Options): RequestHandler;
 
     /**
      * Transform the HTTP headers of the response.
-     * @param {Transform} fn A transformation function.
-     * @return {any} The body.
+     * @param {TransformHeader} fn A transformation function.
+     * @return {RequestHandler} Middleware to transform the headers
      */
-    export function headers(fn: TransformHeader): any;
+    export function headers(fn: TransformHeader): RequestHandler;
 
     /**
-     * Transform the HTTP headers of the response.
-     * @param {Transform} fn A transformation function.
-     * @return {any} The body.
+     * Asynchronously transform the HTTP headers of the response.
+     * @param {TransformHeaderAsync} fn A transformation function.
+     * @return {RequestHandler} Middleware to transform the headers
      */
-    export function headersAsync(fn: TransformHeader): PromiseLike<any>;
+    export function headersAsync(fn: TransformHeaderAsync): RequestHandler;
+
+    /**
+     * Transform chunks as they are written to the response
+     * @param {TransformChunk} fn A transformation function.
+     * @param {Options} [options] Write options.
+     * @return {RequestHandler} Middleware to transform chunks.
+     */
+    export function write(fn: TransformChunk, options?: Options): RequestHandler;
 }
diff --git a/types/express-mung/tsconfig.json b/types/express-mung/tsconfig.json
index 9dd04b84e6..1588655c88 100644
--- a/types/express-mung/tsconfig.json
+++ b/types/express-mung/tsconfig.json
@@ -6,7 +6,7 @@
         ],
         "noImplicitAny": true,
         "noImplicitThis": true,
-        "strictNullChecks": false,
+        "strictNullChecks": true,
         "strictFunctionTypes": true,
         "baseUrl": "../",
         "typeRoots": [
@@ -20,4 +20,4 @@
         "index.d.ts",
         "express-mung-tests.ts"
     ]
-}
\ No newline at end of file
+}