diff --git a/aio/content/examples/testing/src/testing/activated-route-stub.ts b/aio/content/examples/testing/src/testing/activated-route-stub.ts
index 3303f8d58c..59fec15af7 100644
--- a/aio/content/examples/testing/src/testing/activated-route-stub.ts
+++ b/aio/content/examples/testing/src/testing/activated-route-stub.ts
@@ -21,8 +21,8 @@ export class ActivatedRouteStub {
   /** The mock paramMap observable */
   readonly paramMap = this.subject.asObservable();
 
-  /** Set the paramMap observables's next value */
-  setParamMap(params?: Params) {
+  /** Set the paramMap observable's next value */
+  setParamMap(params: Params = {}) {
     this.subject.next(convertToParamMap(params));
   }
 }