diff --git a/gulpfile.js b/gulpfile.js
index 04e8c07..d718abc 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -15,14 +15,14 @@ gulp.task('jsonlint', function () {
 });
 
 gulp.task('jshint', function () {
-  return gulp.src(['src/**/*.js', 'test/**/*.js'])
+  return gulp.src(['src/**/*.js', 'test/**/*.js', 'gulpfile.js'])
     .pipe(jshint())
     .pipe(jshint.reporter('jshint-stylish'))
     .pipe(jshint.reporter('fail'));
 });
 
 gulp.task('jscs', function () {
-  return gulp.src(['src/**/*.js', 'test/**/*.js'])
+  return gulp.src(['src/**/*.js', 'test/**/*.js', 'gulpfile.js'])
     .pipe(jscs())
     .pipe(jscs.reporter())
     .pipe(jscs.reporter('fail'));
@@ -33,8 +33,8 @@ gulp.task('mocha', function () {
     .pipe(gMocha());
 });
 
-gulp.task('watch', function() {
-  gulp.watch(['src/**/*.js'], ['default']);
+gulp.task('watch', function () {
+  return gulp.watch(['src/**/*.js'], ['default']);
 });
 
 gulp.task('default', function () {
@@ -42,6 +42,7 @@ gulp.task('default', function () {
     // If you want details of the error in the console
     console.warn(error.toString());
     console.warn(error.message);
+
     // jshint validthis: true
     this.emit('end');
   }
@@ -50,7 +51,7 @@ gulp.task('default', function () {
   gulp.src(['src/**/*.json'])
     .pipe(gulp.dest('lib'));
 
-  return gulp.src([ 'src/**/*.js' ])
+  return gulp.src(['src/**/*.js'])
     .pipe(sourcemaps.init())
     .pipe(babel({
       presets: ['es2015-node4'],
@@ -66,4 +67,4 @@ gulp.task('default', function () {
 // Aliases
 gulp.task('validate', ['jsonlint', 'jshint', 'jscs']);
 gulp.task('test', gSequence('validate', 'mocha'));
-gulp.task('build', ['default']);
\ No newline at end of file
+gulp.task('build', ['default']);
diff --git a/src/Request.js b/src/Request.js
index 2b65e0a..ec7cc51 100644
--- a/src/Request.js
+++ b/src/Request.js
@@ -131,8 +131,8 @@ export default class Request {
         throw new Error('Incompatible auth data', options.auth);
       }
 
-      var user = options.auth.user || options.auth.username;
-      var password = options.auth.pass || options.auth.password;
+      const user = options.auth.user || options.auth.username;
+      const password = options.auth.pass || options.auth.password;
 
       transOpts.auth = user + ':' + password;
     }
@@ -150,7 +150,7 @@ export default class Request {
   createResponse(response, body) {
     // Handle the few known special cases
     if (this.options.json) {
-      var str = body.toString();
+      const str = body.toString();
       if (str.length !== 0) {
         body = JSON.parse(str);
       } else {
diff --git a/src/StreamReader.js b/src/StreamReader.js
index 1b303a0..42df71d 100644
--- a/src/StreamReader.js
+++ b/src/StreamReader.js
@@ -45,8 +45,8 @@ export default class StreamReader extends stream.Writable {
    * @return Buffer containing the stream contents
    */
   readAll() {
-    var resolve;
-    var reject;
+    let resolve;
+    let reject;
     let handleData;
     let handleFinished;
     let handleError;
diff --git a/test/RequestErrorSpec.js b/test/RequestErrorSpec.js
index 36e82d0..bcb9eba 100644
--- a/test/RequestErrorSpec.js
+++ b/test/RequestErrorSpec.js
@@ -1,12 +1,16 @@
+// jshint -W034
+// Node needs the declaration to permit usage of 'let' */
+'use strict';
+
 const expect = require('chai').expect;
 const RequestError = require('../lib/RequestError');
 
 describe('RequestError', () => {
 
-  var message = 'foo';
-  var status = 303;
-  var response = { foo: 'bar' };
-  var error = new RequestError(message, status, response);
+  let message = 'foo';
+  let status = 303;
+  let response = { foo: 'bar' };
+  let error = new RequestError(message, status, response);
 
   it('Supports message, status code and response', () => {
     expect(error.message).to.equal(message);
diff --git a/test/RequestSpec.js b/test/RequestSpec.js
index 066493f..5641b16 100644
--- a/test/RequestSpec.js
+++ b/test/RequestSpec.js
@@ -1,13 +1,17 @@
+// jshint -W034
+// Node needs the declaration to permit usage of 'let' */
+'use strict';
+
 const expect = require('chai').expect;
 const Request = require('../lib/Request');
 
 describe('Request - test against httpbin.org', () => {
 
-  var request;
-  var url;
-  var headers;
-  var body;
-  var auth;
+  let request;
+  let url;
+  let headers;
+  let body;
+  let auth;
 
   it('Supports HTTP', () => {
     url = 'http://httpbin.org/get';
diff --git a/test/StreamReaderSpec.js b/test/StreamReaderSpec.js
index fc16d64..d2f0b35 100644
--- a/test/StreamReaderSpec.js
+++ b/test/StreamReaderSpec.js
@@ -1,3 +1,7 @@
+// jshint -W034
+// Node needs the declaration to permit usage of 'let' */
+'use strict';
+
 const path = require('path');
 const fs = require('fs');
 const util = require('util');
@@ -9,13 +13,13 @@ const StreamReader = require('../lib/StreamReader');
 describe('StreamReader', () => {
 
   it('Reads a stream fully', () => {
-    var filePath = path.resolve(__dirname, './fixtures/sample.json');
-    var stream = fs.createReadStream(filePath);
-    var reader = new StreamReader(stream);
+    let filePath = path.resolve(__dirname, './fixtures/sample.json');
+    let stream = fs.createReadStream(filePath);
+    let reader = new StreamReader(stream);
 
     return reader.readAll()
       .then((output) => {
-        var str = output.toString();
+        let str = output.toString();
 
         expect(str).to.equal(JSON.stringify(fixture, null, 2));
       });
@@ -31,9 +35,9 @@ describe('StreamReader', () => {
     };
 
     util.inherits(MockStream, stream.Readable);
-    var mock = new MockStream();
-    var reader = new StreamReader(mock);
-    var err = new Error('Bogus error');
+    let mock = new MockStream();
+    let reader = new StreamReader(mock);
+    let err = new Error('Bogus error');
     process.nextTick(() => {
       reader.emit('error', err);
     });
diff --git a/test/indexSpec.js b/test/indexSpec.js
index 4e79116..1684261 100644
--- a/test/indexSpec.js
+++ b/test/indexSpec.js
@@ -1,3 +1,7 @@
+// jshint -W034
+// Node needs the declaration to permit usage of 'let' */
+'use strict';
+
 const path = require('path');
 const fs = require('fs');
 const expect = require('chai').expect;
@@ -12,21 +16,21 @@ describe('index.js wrapper', () => {
   );
 
   it('Nested classes - request.Request', () => {
-    var url = 'https://httpbin.org/get';
-    var req = new request.Request('GET', url, { json: true });
+    let url = 'https://httpbin.org/get';
+    let req = new request.Request('GET', url, { json: true });
 
     return req.run()
       .then((response) => expect(response).to.exist);
   });
 
   it('Nested classes - request.StreamReader', () => {
-    var filePath = path.resolve(__dirname, './fixtures/sample.json');
-    var stream = fs.createReadStream(filePath);
-    var reader = new request.StreamReader(stream);
+    let filePath = path.resolve(__dirname, './fixtures/sample.json');
+    let stream = fs.createReadStream(filePath);
+    let reader = new request.StreamReader(stream);
 
     return reader.readAll()
       .then((output) => {
-        var str = output.toString();
+        let str = output.toString();
 
         expect(str).to.equal(JSON.stringify(fixture, null, 2));
       });