diff --git a/lib/defaults.js b/lib/defaults.js
index 069f155..9d516e8 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -9,6 +9,9 @@ var DEFAULT_CONTENT_TYPE = {
 
 module.exports = {
   transformRequest: [function (data, headers) {
+    if(utils.isFormData(data)) {
+      return data;
+    }
     if (utils.isArrayBuffer(data)) {
       return data;
     }