diff --git a/src/rpc/channels.ts b/src/rpc/channels.ts
index 2045ee3c92..80c63b12d8 100644
--- a/src/rpc/channels.ts
+++ b/src/rpc/channels.ts
@@ -1591,9 +1591,11 @@ export type WorkerInitializer = {
   url: string,
 };
 export interface WorkerChannel extends Channel {
+  on(event: 'close', callback: (params: WorkerCloseEvent) => void): this;
   evaluateExpression(params: WorkerEvaluateExpressionParams): Promise<WorkerEvaluateExpressionResult>;
   evaluateExpressionHandle(params: WorkerEvaluateExpressionHandleParams): Promise<WorkerEvaluateExpressionHandleResult>;
 }
+export type WorkerCloseEvent = {};
 export type WorkerEvaluateExpressionParams = {
   expression: string,
   isFunction: boolean,
diff --git a/src/rpc/client/browserServer.ts b/src/rpc/client/browserServer.ts
index 79b730ec55..bf917c75bd 100644
--- a/src/rpc/client/browserServer.ts
+++ b/src/rpc/client/browserServer.ts
@@ -50,6 +50,4 @@ export class BrowserServer extends ChannelOwner<BrowserServerChannel, BrowserSer
       await this._channel.close();
     });
   }
-
-  _checkLeaks() {}
 }
diff --git a/src/rpc/protocol.yml b/src/rpc/protocol.yml
index d837e088ba..7f68198a86 100644
--- a/src/rpc/protocol.yml
+++ b/src/rpc/protocol.yml
@@ -1343,6 +1343,9 @@ Worker:
       returns:
         handle: JSHandle
 
+  events:
+
+    close:
 
 
 JSHandle:
diff --git a/test/browsertype-connect.spec.ts b/test/browsertype-connect.spec.ts
index cb378d7e6a..0d6cb2057c 100644
--- a/test/browsertype-connect.spec.ts
+++ b/test/browsertype-connect.spec.ts
@@ -18,7 +18,7 @@
 import utils from './utils';
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
-it.slow()('should be able to reconnect to a browser', async({browserType, defaultBrowserOptions, server}) => {
+it.slow()('should be able to reconnect to a browser', async({browserType, defaultBrowserOptions, server, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   {
     const browser = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
@@ -34,26 +34,29 @@ it.slow()('should be able to reconnect to a browser', async({browserType, defaul
     await page.goto(server.EMPTY_PAGE);
     await browser.close();
   }
-  await (browserServer as any)._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
-it.fail(USES_HOOKS || (CHROMIUM && WIN)).slow()('should handle exceptions during connect', async({browserType, defaultBrowserOptions, server}) => {
+it.fail(USES_HOOKS || (CHROMIUM && WIN)).slow()('should handle exceptions during connect', async({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const __testHookBeforeCreateBrowser = () => { throw new Error('Dummy') };
   const error = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint(), __testHookBeforeCreateBrowser } as any).catch(e => e);
-  await (browserServer as any)._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
   expect(error.message).toContain('Dummy');
 });
 
-it('should set the browser connected state', async ({browserType, defaultBrowserOptions}) => {
+it('should set the browser connected state', async ({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const remote = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
   expect(remote.isConnected()).toBe(true);
   await remote.close();
   expect(remote.isConnected()).toBe(false);
-  await (browserServer as any)._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
diff --git a/test/browsertype-launch-server.spec.js b/test/browsertype-launch-server.spec.js
index cc30fb15ab..4f6b0fde46 100644
--- a/test/browsertype-launch-server.spec.js
+++ b/test/browsertype-launch-server.spec.js
@@ -20,7 +20,7 @@ const fs = require('fs');
 const utils = require('./utils');
 const {FFOX, CHROMIUM, WEBKIT, WIN, USES_HOOKS, CHANNEL} = testOptions;
 
-it('should work', async({browserType, defaultBrowserOptions}) => {
+it('should work', async({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const browser = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
   const browserContext = await browser.newContext();
@@ -30,7 +30,8 @@ it('should work', async({browserType, defaultBrowserOptions}) => {
   expect(await page.evaluate('11 * 11')).toBe(121);
   await page.close();
   await browser.close();
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
@@ -76,7 +77,7 @@ it('should fire close event', async ({browserType, defaultBrowserOptions}) => {
   expect(result.signal).toBe(null);
 });
 
-it('should reject navigation when browser closes', async({browserType, defaultBrowserOptions, server}) => {
+it('should reject navigation when browser closes', async({browserType, defaultBrowserOptions, server, toImpl}) => {
   server.setRoute('/one-style.css', () => {});
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const remote = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
@@ -86,11 +87,12 @@ it('should reject navigation when browser closes', async({browserType, defaultBr
   await remote.close();
   const error = await navigationPromise;
   expect(error.message).toContain('Navigation failed because page was closed!');
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
-it('should reject waitForSelector when browser closes', async({browserType, defaultBrowserOptions, server}) => {
+it('should reject waitForSelector when browser closes', async({browserType, defaultBrowserOptions, server, toImpl}) => {
   server.setRoute('/empty.html', () => {});
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const remote = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
@@ -103,18 +105,20 @@ it('should reject waitForSelector when browser closes', async({browserType, defa
   await remote.close();
   const error = await watchdog;
   expect(error.message).toContain('Protocol error');
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
-it('should throw if used after disconnect', async({browserType, defaultBrowserOptions}) => {
+it('should throw if used after disconnect', async({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const remote = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
   const page = await remote.newPage();
   await remote.close();
   const error = await page.evaluate('1 + 1').catch(e => e);
   expect(error.message).toContain('has been closed');
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
diff --git a/test/multiclient.spec.js b/test/multiclient.spec.js
index d30e32479e..1f378527d8 100644
--- a/test/multiclient.spec.js
+++ b/test/multiclient.spec.js
@@ -17,7 +17,7 @@
 
 const {FFOX, CHROMIUM, WEBKIT} = testOptions;
 
-it('should work across sessions', async ({browserType, defaultBrowserOptions}) => {
+it('should work across sessions', async ({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const browser1 = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
   expect(browser1.contexts().length).toBe(0);
@@ -34,7 +34,8 @@ it('should work across sessions', async ({browserType, defaultBrowserOptions}) =
   await browser1.close();
   await browser2.close();
 
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
@@ -72,7 +73,7 @@ it.slow()('should be emitted when: browser gets closed, disconnected or underlyi
   expect(disconnectedRemote2).toBe(1);
 });
 
-it('should be able to connect multiple times to the same browser', async({browserType, defaultBrowserOptions}) => {
+it('should be able to connect multiple times to the same browser', async({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   const browser1 = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
   const browser2 = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
@@ -83,11 +84,12 @@ it('should be able to connect multiple times to the same browser', async({browse
   const page2 = await browser2.newPage();
   expect(await page2.evaluate(() => 7 * 6)).toBe(42, 'original browser should still work');
   await browser2.close();
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });
 
-it('should not be able to close remote browser', async({browserType, defaultBrowserOptions}) => {
+it('should not be able to close remote browser', async({browserType, defaultBrowserOptions, toImpl}) => {
   const browserServer = await browserType.launchServer(defaultBrowserOptions);
   {
     const remote = await browserType.connect({ wsEndpoint: browserServer.wsEndpoint() });
@@ -99,6 +101,7 @@ it('should not be able to close remote browser', async({browserType, defaultBrow
     await remote.newContext();
     await remote.close();
   }
-  await browserServer._checkLeaks();
+  if (toImpl)
+    await toImpl(browserServer)._checkLeaks();
   await browserServer.close();
 });