diff --git a/index.js b/index.js
index 47993ac..9ee9889 100644
--- a/index.js
+++ b/index.js
@@ -42,7 +42,7 @@ function createXHR(options, callback) {
 
         return body
     }
-    
+
     var failureResponse = {
                 body: undefined,
                 headers: {},
@@ -51,7 +51,7 @@ function createXHR(options, callback) {
                 url: uri,
                 rawRequest: xhr
             }
-    
+
     function errorFunc(evt) {
         clearTimeout(timeoutTimer)
         if(!(evt instanceof Error)){
@@ -74,7 +74,7 @@ function createXHR(options, callback) {
         }
         var response = failureResponse
         var err = null
-        
+
         if (status !== 0){
             response = {
                 body: getBody(),
@@ -91,9 +91,9 @@ function createXHR(options, callback) {
             err = new Error("Internal XMLHttpRequest Error")
         }
         callback(err, response, response.body)
-        
+
     }
-    
+
     if (typeof options === "string") {
         options = { uri: options }
     }
@@ -128,7 +128,7 @@ function createXHR(options, callback) {
         isJson = true
         headers["accept"] || headers["Accept"] || (headers["Accept"] = "application/json") //Don't override existing accept header declared by user
         if (method !== "GET" && method !== "HEAD") {
-            headers["Content-Type"] = "application/json"
+            headers["content-type"] || headers["Content-Type"] || (headers["Content-Type"] = "application/json") //Don't override existing accept header declared by user
             body = JSON.stringify(options.json)
         }
     }
@@ -170,8 +170,8 @@ function createXHR(options, callback) {
     if ("responseType" in options) {
         xhr.responseType = options.responseType
     }
-    
-    if ("beforeSend" in options && 
+
+    if ("beforeSend" in options &&
         typeof options.beforeSend === "function"
     ) {
         options.beforeSend(xhr)