diff --git a/src/client.ts b/src/client.ts
index 1990c2b06..e0095e675 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -12,7 +12,7 @@ import * as _ from 'lodash';
 import * as request from 'request';
 import { v4 as uuidv4 } from 'uuid';
 import { HttpClient, Request } from './http';
-import { IHeaders, IOptions, ISecurity, SoapMethod, SoapMethodAsync } from './types';
+import { IHeaders, IHttpClient, IOptions, ISecurity, SoapMethod, SoapMethodAsync } from './types';
 import { findPrefix } from './utils';
 import { WSDL } from './wsdl';
 import { IPort, OperationElement, ServiceElement } from './wsdl/elements';
@@ -56,7 +56,7 @@ export class Client extends EventEmitter {
   public lastElapsedTime?: number;
 
   private wsdl: WSDL;
-  private httpClient: HttpClient;
+  private httpClient: IHttpClient;
   private soapHeaders: any[];
   private httpHeaders: IHeaders;
   private bodyAttributes: string[];
diff --git a/src/http.ts b/src/http.ts
index c712d2ba1..efb4f2f8e 100644
--- a/src/http.ts
+++ b/src/http.ts
@@ -8,15 +8,11 @@ import * as httpNtlm from 'httpntlm';
 import * as req from 'request';
 import * as url from 'url';
 import {v4 as uuidv4} from 'uuid';
-import { IHeaders, IOptions } from './types';
+import { IExOptions, IHeaders, IHttpClient, IOptions } from './types';
 
 const debug = debugBuilder('node-soap');
 const VERSION = require('../package.json').version;
 
-export interface IExOptions {
-  [key: string]: any;
-}
-
 export interface IAttachment {
   name: string;
   contentId: string;
@@ -33,7 +29,7 @@ export type Request = req.Request;
  *
  * @constructor
  */
-export class HttpClient {
+export class HttpClient implements IHttpClient {
   private _request: req.RequestAPI<req.Request, req.CoreOptions, req.Options>;
 
   constructor(options?: IOptions) {
diff --git a/src/types.ts b/src/types.ts
index f657042e2..09fa634ca 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,11 +1,19 @@
 
 import * as req from 'request';
-import { HttpClient } from './http';
 
 export interface IHeaders {
   [k: string]: any;
 }
 
+export interface IExOptions {
+  [key: string]: any;
+}
+
+export interface IHttpClient {
+  request(rurl: string, data: any, callback: (error: any, res?: any, body?: any) => any, exheaders?: IHeaders, exoptions?: IExOptions, caller?);
+  requestStream?(rurl: string, data: any, exheaders?: IHeaders, exoptions?: IExOptions, caller?): req.Request;
+}
+
 /** @deprecated use SoapMethod */
 export type ISoapMethod = SoapMethod;
 export type SoapMethod = (
@@ -112,7 +120,7 @@ export interface IOptions extends IWsdlBaseOptions {
   /** set specific key instead of <pre><soap:Body></soap:Body></pre>. */
   envelopeKey?: string;
   /** provide your own http client that implements request(rurl, data, callback, exheaders, exoptions) */
-  httpClient?: HttpClient;
+  httpClient?: IHttpClient;
   /** override the request module. */
   request?: req.RequestAPI<req.Request, req.CoreOptions, req.RequiredUriUrl>;
   stream?: boolean;