diff --git a/packages/playwright/src/isomorphic/testServerConnection.ts b/packages/playwright/src/isomorphic/testServerConnection.ts
index 2cee3eb161..00dafdf20b 100644
--- a/packages/playwright/src/isomorphic/testServerConnection.ts
+++ b/packages/playwright/src/isomorphic/testServerConnection.ts
@@ -32,7 +32,7 @@ export interface TestServerTransport {
 export class WebSocketTestServerTransport implements TestServerTransport {
   private _ws: WebSocket;
 
-  constructor(url: URL) {
+  constructor(url: string | URL) {
     this._ws = new WebSocket(url);
   }
 
diff --git a/tests/playwright-test/test-server-connection.spec.ts b/tests/playwright-test/test-server-connection.spec.ts
index af5f0223e5..aef2b63483 100644
--- a/tests/playwright-test/test-server-connection.spec.ts
+++ b/tests/playwright-test/test-server-connection.spec.ts
@@ -15,13 +15,13 @@
  */
 import { test as baseTest, expect } from './ui-mode-fixtures';
 
-import { TestServerConnection } from '../../packages/playwright/lib/isomorphic/testServerConnection';
+import { TestServerConnection, WebSocketTestServerTransport } from '../../packages/playwright/lib/isomorphic/testServerConnection';
 
 class TestServerConnectionUnderTest extends TestServerConnection {
   events: [string, any][] = [];
 
   constructor(wsUrl: string) {
-    super(wsUrl);
+    super(new WebSocketTestServerTransport(wsUrl));
     this.onTestFilesChanged(params => this.events.push(['testFilesChanged', params]));
     this.onStdio(params => this.events.push(['stdio', params]));
     this.onLoadTraceRequested(params => this.events.push(['loadTraceRequested', params]));