diff --git a/packages/core/src/util/lang.ts b/packages/core/src/util/lang.ts
index d539183af5..b6631e84d0 100644
--- a/packages/core/src/util/lang.ts
+++ b/packages/core/src/util/lang.ts
@@ -21,6 +21,7 @@ export function isPromise(obj: any): obj is Promise<any> {
  * Determine if the argument is an Observable
  */
 export function isObservable(obj: any | Observable<any>): obj is Observable<any> {
-  // TODO: use Symbol.observable when https://github.com/ReactiveX/rxjs/issues/2415 will be resolved
+  // TODO: use isObservable once we update pass rxjs 6.1
+  // https://github.com/ReactiveX/rxjs/blob/master/CHANGELOG.md#610-2018-05-03
   return !!obj && typeof obj.subscribe === 'function';
 }
diff --git a/packages/core/src/view/provider.ts b/packages/core/src/view/provider.ts
index ffd2c3966a..83e046ce53 100644
--- a/packages/core/src/view/provider.ts
+++ b/packages/core/src/view/provider.ts
@@ -13,6 +13,7 @@ import {TemplateRef} from '../linker/template_ref';
 import {ViewContainerRef} from '../linker/view_container_ref';
 import {Renderer as RendererV1, Renderer2} from '../render/api';
 import {stringify} from '../util';
+import {isObservable} from '../util/lang';
 
 import {createChangeDetectorRef, createInjector, createRendererV1} from './refs';
 import {BindingDef, BindingFlags, DepDef, DepFlags, NodeDef, NodeFlags, OutputDef, OutputType, ProviderData, QueryValueType, Services, ViewData, ViewFlags, ViewState, asElementData, asProviderData, shouldCallLifecycleInitHook} from './types';
@@ -138,7 +139,7 @@ export function createDirectiveInstance(view: ViewData, def: NodeDef): any {
     for (let i = 0; i < def.outputs.length; i++) {
       const output = def.outputs[i];
       const outputObservable = instance[output.propName !];
-      if (typeof outputObservable === 'object') {
+      if (isObservable(outputObservable)) {
         const subscription = outputObservable.subscribe(
             eventHandlerClosure(view, def.parent !.nodeIndex, output.eventName));
         view.disposables ![def.outputIndex + i] = subscription.unsubscribe.bind(subscription);
diff --git a/packages/core/test/linker/integration_spec.ts b/packages/core/test/linker/integration_spec.ts
index fca61d50e2..3a6d125297 100644
--- a/packages/core/test/linker/integration_spec.ts
+++ b/packages/core/test/linker/integration_spec.ts
@@ -347,17 +347,18 @@ function declareTests({useJit}: {useJit: boolean}) {
       });
 
       it('should display correct error message for uninitialized @Output', () => {
-        @Directive({selector: '[uninitializedOuput]'})
-        class UninitializedOuput {
-          @Output() customEvent;
-          doSomething() {
-          }
+        @Component({selector: 'my-uninitialized-output', template: '<p>It works!</p>'})
+        class UninitializedOutputComp {
+          @Output() customEvent !: EventEmitter<any>;
         }
 
-        TestBed.configureTestingModule({declarations: [MyComp, UninitializedOuput]});
-        const template = '<p (customEvent)="doNothing()"></p>';
+        const template =
+            '<my-uninitialized-output (customEvent)="doNothing()"></my-uninitialized-output>';
         TestBed.overrideComponent(MyComp, {set: {template}});
-        TestBed.createComponent(MyComp).toThrowError('@Output customEvent not initialized in \'UninitializedOuput\'.');
+
+        TestBed.configureTestingModule({declarations: [MyComp, UninitializedOutputComp]});
+        expect(() => TestBed.createComponent(MyComp))
+            .toThrowError('@Output customEvent not initialized in \'UninitializedOutputComp\'.');
       });
 
       it('should read directives metadata from their binding token', () => {