diff --git a/lib/defaults.js b/lib/defaults.js
index 7aa1641..3baa22f 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -5,12 +5,12 @@ var utils = require('./utils');
 var JSON_START = /^\s*(\[|\{[^\{])/;
 var JSON_END = /[\}\]]\s*$/;
 var PROTECTION_PREFIX = /^\)\]\}',?\n/;
-var CONTENT_TYPE_APPLICATION_JSON = {
-  'Content-Type': 'application/json;charset=utf-8'
+var DEFAULT_CONTENT_TYPE = {
+  'Content-Type': 'application/x-www-form-urlencoded'
 };
 
 module.exports = {
-  transformRequest: [function (data) {
+  transformRequest: [function (data, headers) {
     if (utils.isArrayBuffer(data)) {
       return data;
     }
@@ -18,6 +18,10 @@ module.exports = {
       return data.buffer;
     }
     if (utils.isObject(data) && !utils.isFile(data) && !utils.isBlob(data)) {
+      // Set application/json if no Content-Type has been specified
+      if (utils.isUndefined(headers['Content-Type'])) {
+        headers['Content-Type'] = 'application/json;charset=utf-8';
+      }
       return JSON.stringify(data);
     }
     return data;
@@ -37,9 +41,9 @@ module.exports = {
     common: {
       'Accept': 'application/json, text/plain, */*'
     },
-    patch: utils.merge(CONTENT_TYPE_APPLICATION_JSON),
-    post: utils.merge(CONTENT_TYPE_APPLICATION_JSON),
-    put: utils.merge(CONTENT_TYPE_APPLICATION_JSON)
+    patch: utils.merge(DEFAULT_CONTENT_TYPE),
+    post: utils.merge(DEFAULT_CONTENT_TYPE),
+    put: utils.merge(DEFAULT_CONTENT_TYPE)
   },
 
   xsrfCookieName: 'XSRF-TOKEN',