diff --git a/test/js-specs.js b/test/js-specs.js
index 253841e..67343a8 100644
--- a/test/js-specs.js
+++ b/test/js-specs.js
@@ -419,7 +419,7 @@ describe('Common helpers', function () {
         response => response.data.should.be.equal('fakeData')
       );
 
-     handler({ data: 'fakeData' });
+      handler({ data: 'fakeData' });
     });
 
     it('does not change response data if response type is "text"', () => {
@@ -449,7 +449,7 @@ describe('Common helpers', function () {
       const helpers = require('../www/helpers')(null, jsUtil, null, messages, null, errorCodes);
       const handler = helpers.injectRawResponseHandler(
         'json',
-        response => should.equal(null, response.data)
+        response => should.equal(undefined, response.data)
       );
 
       handler({ data: emptyData });
@@ -486,7 +486,7 @@ describe('Common helpers', function () {
         }
       );
 
-      handler({ data: 'myString', headers: { 'content-type': 'fakeType'} });
+      handler({ data: 'myString', headers: { 'content-type': 'fakeType' } });
     });
 
     it('handles empty "blob" response correctly', () => {
@@ -498,7 +498,7 @@ describe('Common helpers', function () {
         }
       );
 
-      handler({ data: '', headers: { 'content-type': 'fakeType'} });
+      handler({ data: '', headers: { 'content-type': 'fakeType' } });
     });
 
     it('calls failure callback when post-processing fails', () => {
@@ -579,7 +579,7 @@ describe('Common helpers', function () {
 
     it('processes data correctly when serializer "utf8" is configured', (cb) => {
       helpers.processData('myString', 'utf8', (data) => {
-        data.should.be.eql({text: 'myString'});
+        data.should.be.eql({ text: 'myString' });
         cb();
       })
     });
@@ -624,7 +624,7 @@ describe('Common helpers', function () {
     });
 
     it('processes data correctly when serializer "raw" is configured', (cb) => {
-      const byteArray = new Uint8Array([1,2,3]);
+      const byteArray = new Uint8Array([1, 2, 3]);
       helpers.processData(byteArray, 'raw', (data) => {
         data.should.be.a('ArrayBuffer');
         data.should.be.equal(byteArray.buffer);
@@ -680,7 +680,7 @@ describe('Dependency Validator', function () {
   describe('checkFormDataInstance()', function () {
     it('throws an error if FormData.entries() is not supported on given instance', function () {
       const console = new ConsoleMock();
-      const validator = require('../www/dependency-validator')({ FormData: {}}, console, messages);
+      const validator = require('../www/dependency-validator')({ FormData: {} }, console, messages);
 
       (() => validator.checkFormDataInstance({})).should.throw(messages.MISSING_FORMDATA_ENTRIES_API);
     });
@@ -717,12 +717,12 @@ describe('Ponyfills', function () {
         const iterator = new ponyfills.Iterator([]);
         iterator.next().should.be.eql({ done: true, value: undefined });
       });
-  
+
       it('returns iteration object correctly when end posititon of list is not reached yet', () => {
         const iterator = new ponyfills.Iterator([['first', 'this is the first item']]);
         iterator.next().should.be.eql({ done: false, value: ['first', 'this is the first item'] });
       });
-  
+
       it('returns iteration object correctly when end posititon of list is already reached', () => {
         const iterator = new ponyfills.Iterator([['first', 'this is the first item']]);
         iterator.next();
diff --git a/www/helpers.js b/www/helpers.js
index 66e20aa..a578211 100644
--- a/www/helpers.js
+++ b/www/helpers.js
@@ -292,29 +292,31 @@ module.exports = function init(global, jsUtil, cookieHandler, messages, base64,
         return success(response);
       }
 
-      if (!response.data) {
-        // return null as data if response data is not set
-        response.data = null;
-        return success(response);
-      }
-
       try {
         // json
         if (responseType === validResponseTypes[1]) {
-          response.data = JSON.parse(response.data);
+          response.data = response.data === ''
+            ? undefined
+            : JSON.parse(response.data);
         }
 
         // arraybuffer
         else if (responseType === validResponseTypes[2]) {
-          response.data = base64.toArrayBuffer(response.data);
+          response.data = response.data === ''
+            ? null
+            : base64.toArrayBuffer(response.data);
         }
 
         // blob
         else if (responseType === validResponseTypes[3]) {
-          var buffer = base64.toArrayBuffer(response.data);
-          var type = response.headers['content-type'] || '';
-          var blob = new Blob([ buffer ], { type: type });
-          response.data = blob;
+          if (response.data === '') {
+            response.data = null;
+          } else {
+            var buffer = base64.toArrayBuffer(response.data);
+            var type = response.headers['content-type'] || '';
+            var blob = new Blob([buffer], { type: type });
+            response.data = blob;
+          }
         }
 
         success(response);
@@ -390,7 +392,7 @@ module.exports = function init(global, jsUtil, cookieHandler, messages, base64,
     if (allowedInstanceTypes) {
       var isCorrectInstanceType = false;
 
-      allowedInstanceTypes.forEach(function(type) {
+      allowedInstanceTypes.forEach(function (type) {
         if ((global[type] && data instanceof global[type]) || (ponyfills[type] && data instanceof ponyfills[type])) {
           isCorrectInstanceType = true;
         }
@@ -446,7 +448,7 @@ module.exports = function init(global, jsUtil, cookieHandler, messages, base64,
     if (entry.value[1] instanceof global.Blob || entry.value[1] instanceof global.File) {
       var reader = new global.FileReader();
 
-      reader.onload = function() {
+      reader.onload = function () {
         result.buffers.push(base64.fromArrayBuffer(reader.result));
         result.names.push(entry.value[0]);
         result.fileNames.push(entry.value[1].name || 'blob');