diff --git a/packages/service-worker/worker/src/adapter.ts b/packages/service-worker/worker/src/adapter.ts
index dfd30be040..2e2847d62e 100644
--- a/packages/service-worker/worker/src/adapter.ts
+++ b/packages/service-worker/worker/src/adapter.ts
@@ -43,7 +43,7 @@ export class Adapter {
   /**
    * Extract the pathname of a URL.
    */
-  parseUrl(url: string, relativeTo: string): {origin: string, path: string} {
+  parseUrl(url: string, relativeTo?: string): {origin: string, path: string} {
     const parsed = new URL(url, relativeTo);
     return {origin: parsed.origin, path: parsed.pathname};
   }
diff --git a/packages/service-worker/worker/src/assets.ts b/packages/service-worker/worker/src/assets.ts
index 8776eb1973..19843818f3 100644
--- a/packages/service-worker/worker/src/assets.ts
+++ b/packages/service-worker/worker/src/assets.ts
@@ -69,8 +69,7 @@ export abstract class AssetGroup {
 
     // Determine the origin from the registration scope. This is used to differentiate between
     // relative and absolute URLs.
-    this.origin =
-        this.adapter.parseUrl(this.scope.registration.scope, this.scope.registration.scope).origin;
+    this.origin = this.adapter.parseUrl(this.scope.registration.scope).origin;
   }
 
   async cacheStatus(url: string): Promise<UpdateCacheStatus> {
diff --git a/packages/service-worker/worker/testing/scope.ts b/packages/service-worker/worker/testing/scope.ts
index f357f4da41..265df3c3d6 100644
--- a/packages/service-worker/worker/testing/scope.ts
+++ b/packages/service-worker/worker/testing/scope.ts
@@ -175,7 +175,7 @@ export class SwTestHarness implements ServiceWorkerGlobalScope, Adapter, Context
     }, new MockHeaders());
   }
 
-  parseUrl(url: string, relativeTo: string): {origin: string, path: string} {
+  parseUrl(url: string, relativeTo?: string): {origin: string, path: string} {
     if (typeof URL === 'function') {
       const obj = new URL(url, relativeTo);
       return {origin: obj.origin, path: obj.pathname};