diff --git a/packages/platform-server/src/http.ts b/packages/platform-server/src/http.ts
index 1cd67c7d45..49b07490de 100644
--- a/packages/platform-server/src/http.ts
+++ b/packages/platform-server/src/http.ts
@@ -15,6 +15,14 @@ import {Observable} from 'rxjs/Observable';
 import {Observer} from 'rxjs/Observer';
 import {Subscription} from 'rxjs/Subscription';
 
+const isAbsoluteUrl = /^[a-zA-Z\-\+.]+:\/\//;
+
+function validateRequestUrl(url: string): void {
+  if (!isAbsoluteUrl.test(url)) {
+    throw new Error(`URLs requested via Http on the server must be absolute. URL: ${url}`);
+  }
+}
+
 @Injectable()
 export class ServerXhr implements BrowserXhr {
   build(): XMLHttpRequest { return new xhr2.XMLHttpRequest(); }
@@ -30,6 +38,7 @@ export class ZoneMacroTaskConnection implements Connection {
   lastConnection: Connection;
 
   constructor(public request: Request, backend: XHRBackend) {
+    validateRequestUrl(request.url);
     this.response = new Observable((observer: Observer<Response>) => {
       let task: Task = null;
       let scheduled: boolean = false;
diff --git a/packages/platform-server/test/integration_spec.ts b/packages/platform-server/test/integration_spec.ts
index 4ea5b4f925..1bf08703b4 100644
--- a/packages/platform-server/test/integration_spec.ts
+++ b/packages/platform-server/test/integration_spec.ts
@@ -426,10 +426,10 @@ export function main() {
                NgZone.assertInAngularZone();
                mock.connections.subscribe((mc: MockConnection) => {
                  NgZone.assertInAngularZone();
-                 expect(mc.request.url).toBe('/testing');
+                 expect(mc.request.url).toBe('http://localhost/testing');
                  mc.mockRespond(new Response(new ResponseOptions({body: 'success!', status: 200})));
                });
-               http.get('/testing').subscribe(resp => {
+               http.get('http://localhost/testing').subscribe(resp => {
                  NgZone.assertInAngularZone();
                  expect(resp.text()).toBe('success!');
                });
@@ -449,7 +449,9 @@ export function main() {
                  expect(ref.injector.get(NgZone).hasPendingMacrotasks).toBeTruthy();
                  mc.mockRespond(new Response(new ResponseOptions({body: 'success!', status: 200})));
                });
-               http.get('/testing').subscribe(resp => { expect(resp.text()).toBe('success!'); });
+               http.get('http://localhost/testing').subscribe(resp => {
+                 expect(resp.text()).toBe('success!');
+               });
              });
            });
          }));
@@ -466,7 +468,9 @@ export function main() {
                  expect(ref.injector.get(NgZone).hasPendingMacrotasks).toBeTruthy();
                  mc.mockRespond(new Response(new ResponseOptions({body: 'success!', status: 200})));
                });
-               http.get('/testing').subscribe(resp => { expect(resp.text()).toBe('success!'); });
+               http.get('http://localhost/testing').subscribe(resp => {
+                 expect(resp.text()).toBe('success!');
+               });
              });
            });
          }));
@@ -483,10 +487,22 @@ export function main() {
                  expect(ref.injector.get(NgZone).hasPendingMacrotasks).toBeTruthy();
                  mc.mockRespond(new Response(new ResponseOptions({body: 'success!', status: 200})));
                });
-               http.get('/testing').subscribe(resp => { expect(resp.text()).toBe('success!'); });
+               http.get('http://localhost/testing').subscribe(resp => {
+                 expect(resp.text()).toBe('success!');
+               });
              });
            });
          }));
+      it('throws when given a relative URL', async(() => {
+           const platform = platformDynamicServer(
+               [{provide: INITIAL_CONFIG, useValue: {document: '<app></app>'}}]);
+           platform.bootstrapModule(ExampleModule).then(ref => {
+             const http = ref.injector.get(Http);
+             expect(() => http.get('/testing'))
+                 .toThrowError(
+                     'URLs requested via Http on the server must be absolute. URL: /testing');
+           });
+         }));
     });
   });
 }