diff --git a/modules/@angular/http/src/headers.ts b/modules/@angular/http/src/headers.ts
index 3e582aa239..03906fb3a3 100644
--- a/modules/@angular/http/src/headers.ts
+++ b/modules/@angular/http/src/headers.ts
@@ -49,7 +49,7 @@ export class Headers {
     }
 
     if (headers instanceof Headers) {
-      headers._headers.forEach((values: string[], name: string) => {
+      headers.forEach((values: string[], name: string) => {
         values.forEach(value => this.append(name, value));
       });
       return;
diff --git a/modules/@angular/http/test/backends/xhr_backend_spec.ts b/modules/@angular/http/test/backends/xhr_backend_spec.ts
index 03ee41174d..24edc410e3 100644
--- a/modules/@angular/http/test/backends/xhr_backend_spec.ts
+++ b/modules/@angular/http/test/backends/xhr_backend_spec.ts
@@ -233,9 +233,9 @@ export function main() {
         var connection = new XHRConnection(
             new Request(base.merge(new RequestOptions({headers: headers}))), new MockBrowserXHR());
         connection.response.subscribe();
-        expect(setRequestHeaderSpy).toHaveBeenCalledWith('content-type', 'text/xml');
-        expect(setRequestHeaderSpy).toHaveBeenCalledWith('breaking-bad', '<3');
-        expect(setRequestHeaderSpy).toHaveBeenCalledWith('x-multi', 'a,b');
+        expect(setRequestHeaderSpy).toHaveBeenCalledWith('Content-Type', 'text/xml');
+        expect(setRequestHeaderSpy).toHaveBeenCalledWith('Breaking-Bad', '<3');
+        expect(setRequestHeaderSpy).toHaveBeenCalledWith('X-Multi', 'a,b');
       });
 
       it('should skip content type detection if custom content type header is set', () => {
@@ -246,7 +246,8 @@ export function main() {
             new Request(base.merge(new RequestOptions({body: body, headers: headers}))),
             new MockBrowserXHR());
         connection.response.subscribe();
-        expect(setRequestHeaderSpy).toHaveBeenCalledWith('content-type', 'text/plain');
+        expect(setRequestHeaderSpy).toHaveBeenCalledWith('Content-Type', 'text/plain');
+        expect(setRequestHeaderSpy).not.toHaveBeenCalledWith('Content-Type', 'application/json');
         expect(setRequestHeaderSpy).not.toHaveBeenCalledWith('content-type', 'application/json');
       });
 
@@ -355,7 +356,7 @@ export function main() {
                  new MockBrowserXHR());
              connection.response.subscribe();
              expect(sendSpy).toHaveBeenCalledWith(body);
-             expect(setRequestHeaderSpy).toHaveBeenCalledWith('content-type', 'text/css');
+             expect(setRequestHeaderSpy).toHaveBeenCalledWith('Content-Type', 'text/css');
            });
 
         it('should use array buffer body to the request', () => {
@@ -386,7 +387,7 @@ export function main() {
                  new MockBrowserXHR());
              connection.response.subscribe();
              expect(sendSpy).toHaveBeenCalledWith(body);
-             expect(setRequestHeaderSpy).toHaveBeenCalledWith('content-type', 'text/css');
+             expect(setRequestHeaderSpy).toHaveBeenCalledWith('Content-Type', 'text/css');
            });
       }
 
diff --git a/modules/@angular/http/test/headers_spec.ts b/modules/@angular/http/test/headers_spec.ts
index d1090b82ee..64107463c3 100644
--- a/modules/@angular/http/test/headers_spec.ts
+++ b/modules/@angular/http/test/headers_spec.ts
@@ -76,6 +76,13 @@ export function main() {
         expect(JSON.stringify(headers)).toEqual('{"fOo":["bat"]}');
       });
 
+      it('should preserve cases after cloning', () => {
+        const headers = new Headers();
+        headers.set('fOo', 'baz');
+        headers.set('foo', 'bat');
+        expect(JSON.stringify(new Headers(headers))).toEqual('{"fOo":["bat"]}');
+      });
+
       it('should convert input array to string', () => {
         const headers = new Headers();
         headers.set('foo', ['bar', 'baz']);