diff --git a/apps/tests/xhr-tests.ts b/apps/tests/xhr-tests.ts
index d60c167f3..e7695503b 100644
--- a/apps/tests/xhr-tests.ts
+++ b/apps/tests/xhr-tests.ts
@@ -110,6 +110,17 @@ export var test_XMLHttpRequest_headersSentAndReceivedProperly = function (done)
     // </snippet>
 };
 
+export var test_XMLHttpRequest_setResponseTypeShouldNotThrow = function (done) {
+    try {
+        var xhr = new XMLHttpRequest();
+        (<any>xhr)._setResponseType();
+        done(null);
+    }
+    catch (err) {
+        done(err);
+    }
+};
+
 export var test_XMLHttpRequest_contentSentAndReceivedProperly = function (done) {
     // <snippet module="xhr" title="xhr">
     // ### Send/receive JSON
diff --git a/xhr/xhr.ts b/xhr/xhr.ts
index a20d12bff..9a4fa0951 100644
--- a/xhr/xhr.ts
+++ b/xhr/xhr.ts
@@ -116,11 +116,16 @@ export class XMLHttpRequest {
     }
 
     private _setResponseType() {
-        const contentType = this.getResponseHeader('Content-Type').toLowerCase();
+        const header = this.getResponseHeader('Content-Type');
+        const contentType = header && header.toLowerCase();
 
-        if (contentType.indexOf('application/json') >= 0) {
-            this.responseType = XMLHttpRequestResponseType.json;
-        } else if (contentType.indexOf('text/plain') >= 0) {
+        if (contentType) {
+            if (contentType.indexOf('application/json') >= 0) {
+                this.responseType = XMLHttpRequestResponseType.json;
+            } else if (contentType.indexOf('text/plain') >= 0) {
+                this.responseType = XMLHttpRequestResponseType.text;
+            }
+        } else {
             this.responseType = XMLHttpRequestResponseType.text;
         }
     }
@@ -177,7 +182,7 @@ export class XMLHttpRequest {
             && this._headers
             && this._headers[header]
             && !this._errorFlag
-            ) {
+        ) {
             return this._headers[header];
         }
 
@@ -309,8 +314,8 @@ export class FormData {
     toString(): string {
         var arr = new Array<string>();
 
-        this._data.forEach(function (value, name, map) {
-            arr.push(`${encodeURIComponent(name) }=${encodeURIComponent(value) }`);
+        this._data.forEach(function(value, name, map) {
+            arr.push(`${encodeURIComponent(name)}=${encodeURIComponent(value)}`);
         });
 
         return arr.join("&");