diff --git a/packages/service-worker/worker/src/adapter.ts b/packages/service-worker/worker/src/adapter.ts
index b9d81091f5..08f2d13b38 100644
--- a/packages/service-worker/worker/src/adapter.ts
+++ b/packages/service-worker/worker/src/adapter.ts
@@ -53,7 +53,9 @@ export class Adapter {
    * Extract the pathname of a URL.
    */
   parseUrl(url: string, relativeTo?: string): {origin: string, path: string, search: string} {
-    const parsed = new URL(url, relativeTo);
+    // Workaround a Safari bug, see
+    // https://github.com/angular/angular/issues/31061#issuecomment-503637978
+    const parsed = !relativeTo ? new URL(url) : new URL(url, relativeTo);
     return {origin: parsed.origin, path: parsed.pathname, search: parsed.search};
   }
 
diff --git a/packages/service-worker/worker/testing/scope.ts b/packages/service-worker/worker/testing/scope.ts
index 997b7615cb..0ae7d384a6 100644
--- a/packages/service-worker/worker/testing/scope.ts
+++ b/packages/service-worker/worker/testing/scope.ts
@@ -186,7 +186,7 @@ export class SwTestHarness implements ServiceWorkerGlobalScope, Adapter, Context
 
   parseUrl(url: string, relativeTo?: string): {origin: string, path: string, search: string} {
     const parsedUrl: URL = (typeof URL === 'function') ?
-        new URL(url, relativeTo) :
+        (!relativeTo ? new URL(url) : new URL(url, relativeTo)) :
         require('url').parse(require('url').resolve(relativeTo || '', url));
 
     return {