diff --git a/src/chromium/tsconfig.json b/src/chromium/tsconfig.json
deleted file mode 100644
index 9b96b484ca..0000000000
--- a/src/chromium/tsconfig.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "compilerOptions": {
-    "strict": true
-  },
-  "extends": "../../tsconfig.json"
-}
diff --git a/src/firefox/ffAccessibility.ts b/src/firefox/ffAccessibility.ts
index 39b52d0f49..38e415b7eb 100644
--- a/src/firefox/ffAccessibility.ts
+++ b/src/firefox/ffAccessibility.ts
@@ -14,8 +14,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 import * as accessibility from '../accessibility';
 import { FFSession } from './ffConnection';
+import { Protocol } from './protocol';
 
 export async function getAccessibilityTree(session: FFSession) : Promise<accessibility.AXNode> {
   const { tree } = await session.send('Accessibility.getFullAXTree');
@@ -33,13 +35,13 @@ class FFAXNode implements accessibility.AXNode {
   private _role: string;
   private _cachedHasFocusableChild: boolean|undefined;
 
-  constructor(payload) {
+  constructor(payload: Protocol.AXTree) {
     this._payload = payload;
     this._children = (payload.children || []).map(x => new FFAXNode(x));
-    this._editable = payload.editable;
+    this._editable = !!payload.editable;
     this._richlyEditable = this._editable && (payload.tag !== 'textarea' && payload.tag !== 'input');
-    this._focusable = payload.focusable;
-    this._expanded = payload.expanded;
+    this._focusable = !!payload.focusable;
+    this._expanded = !!payload.expanded;
     this._name = this._payload.name;
     this._role = this._payload.role;
     this._cachedHasFocusableChild;
diff --git a/src/firefox/ffBrowser.ts b/src/firefox/ffBrowser.ts
index 6bf7cb98b7..1d2292cfe1 100644
--- a/src/firefox/ffBrowser.ts
+++ b/src/firefox/ffBrowser.ts
@@ -26,6 +26,7 @@ import { ConnectionTransport, SlowMoTransport } from '../transport';
 import { ConnectionEvents, FFConnection, FFSessionEvents } from './ffConnection';
 import { FFPage } from './ffPage';
 import * as platform from '../platform';
+import { Protocol } from './protocol';
 
 export type FFConnectOptions = {
   slowMo?: number,
@@ -124,12 +125,14 @@ export class FFBrowser extends platform.EventEmitter implements Browser {
     return Array.from(this._targets.values());
   }
 
-  async _onTargetCreated({targetId, url, browserContextId, openerId, type}) {
-    const context = browserContextId ? this._contexts.get(browserContextId) : this._defaultContext;
+  async _onTargetCreated(payload: Protocol.Target.targetCreatedPayload) {
+    const {targetId, url, browserContextId, openerId, type} = payload;
+    const context = browserContextId ? this._contexts.get(browserContextId)! : this._defaultContext;
     const target = new Target(this._connection, this, context, targetId, type, url, openerId);
     this._targets.set(targetId, target);
-    if (target.opener() && target.opener()._pagePromise) {
-      const openerPage = await target.opener()._pagePromise;
+    const opener = target.opener();
+    if (opener && opener._pagePromise) {
+      const openerPage = await opener._pagePromise;
       if (openerPage.listenerCount(Events.Page.Popup)) {
         const popupPage = await target.page();
         openerPage.emit(Events.Page.Popup, popupPage);
@@ -137,14 +140,16 @@ export class FFBrowser extends platform.EventEmitter implements Browser {
     }
   }
 
-  _onTargetDestroyed({targetId}) {
-    const target = this._targets.get(targetId);
+  _onTargetDestroyed(payload: Protocol.Target.targetDestroyedPayload) {
+    const {targetId} = payload;
+    const target = this._targets.get(targetId)!;
     this._targets.delete(targetId);
     target._didClose();
   }
 
-  _onTargetInfoChanged({targetId, url}) {
-    const target = this._targets.get(targetId);
+  _onTargetInfoChanged(payload: Protocol.Target.targetInfoChangedPayload) {
+    const {targetId, url} = payload;
+    const target = this._targets.get(targetId)!;
     target._url = url;
   }
 
@@ -168,14 +173,14 @@ export class FFBrowser extends platform.EventEmitter implements Browser {
         const {targetId} = await this._connection.send('Target.newPage', {
           browserContextId: browserContextId || undefined
         });
-        const target = this._targets.get(targetId);
+        const target = this._targets.get(targetId)!;
         return target.page();
       },
 
       close: async (): Promise<void> => {
         assert(browserContextId, 'Non-incognito profiles cannot be closed!');
-        await this._connection.send('Target.removeBrowserContext', { browserContextId });
-        this._contexts.delete(browserContextId);
+        await this._connection.send('Target.removeBrowserContext', { browserContextId: browserContextId! });
+        this._contexts.delete(browserContextId!);
       },
 
       cookies: async (): Promise<network.NetworkCookie[]> => {
@@ -196,7 +201,7 @@ export class FFBrowser extends platform.EventEmitter implements Browser {
       },
 
       setPermissions: async (origin: string, permissions: string[]): Promise<void> => {
-        const webPermissionToProtocol = new Map([
+        const webPermissionToProtocol = new Map<string, 'geo' | 'microphone' | 'camera' | 'desktop-notifications'>([
           ['geolocation', 'geo'],
           ['microphone', 'microphone'],
           ['camera', 'camera'],
@@ -232,7 +237,7 @@ class Target {
   private readonly _targetId: string;
   private readonly _type: 'page' | 'browser';
   _url: string;
-  private readonly _openerId: string;
+  private readonly _openerId: string | undefined;
 
   constructor(connection: any, browser: FFBrowser, context: BrowserContext, targetId: string, type: 'page' | 'browser', url: string, openerId: string | undefined) {
     this._browser = browser;
@@ -250,7 +255,7 @@ class Target {
   }
 
   opener(): Target | null {
-    return this._openerId ? this._browser._targets.get(this._openerId) : null;
+    return this._openerId ? this._browser._targets.get(this._openerId)! : null;
   }
 
   type(): 'page' | 'browser' {
@@ -266,7 +271,9 @@ class Target {
   }
 
   page(): Promise<Page> {
-    if (this._type === 'page' && !this._pagePromise) {
+    if (this._type !== 'page')
+      throw new Error(`Cannot create page for "${this._type}" target`);
+    if (!this._pagePromise) {
       this._pagePromise = new Promise(async f => {
         const session = await this._connection.createSession(this._targetId);
         this._ffPage = new FFPage(session, this._context);
@@ -291,5 +298,5 @@ export async function createTransport(options: FFConnectOptions): Promise<Connec
     transport = options.transport;
   else if (options.browserWSEndpoint)
     transport = await platform.createWebSocketTransport(options.browserWSEndpoint);
-  return SlowMoTransport.wrap(transport, options.slowMo);
+  return SlowMoTransport.wrap(transport!, options.slowMo);
 }
diff --git a/src/firefox/ffConnection.ts b/src/firefox/ffConnection.ts
index 301cbf19cf..2016b6a4a8 100644
--- a/src/firefox/ffConnection.ts
+++ b/src/firefox/ffConnection.ts
@@ -33,6 +33,12 @@ export class FFConnection extends platform.EventEmitter {
   private _sessions: Map<string, FFSession>;
   _closed: boolean;
 
+  on: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
+  addListener: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
+  off: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
+  removeListener: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
+  once: <T extends keyof Protocol.Events | symbol>(event: T, listener: (payload: T extends symbol ? any : Protocol.Events[T extends keyof Protocol.Events ? T : never]) => void) => this;
+
   constructor(transport: ConnectionTransport) {
     super();
     this._transport = transport;
@@ -43,17 +49,26 @@ export class FFConnection extends platform.EventEmitter {
     this._transport.onclose = this._onClose.bind(this);
     this._sessions = new Map();
     this._closed = false;
+
+    this.on = super.on;
+    this.addListener = super.addListener;
+    this.off = super.removeListener;
+    this.removeListener = super.removeListener;
+    this.once = super.once;
   }
 
   static fromSession(session: FFSession): FFConnection {
-    return session._connection;
+    return session._connection!;
   }
 
   session(sessionId: string): FFSession | null {
     return this._sessions.get(sessionId) || null;
   }
 
-  send(method: string, params: object | undefined = {}): Promise<any> {
+  send<T extends keyof Protocol.CommandParameters>(
+    method: T,
+    params?: Protocol.CommandParameters[T]
+  ): Promise<Protocol.CommandReturnValues[T]> {
     const id = this._rawSend({method, params});
     return new Promise((resolve, reject) => {
       this._callbacks.set(id, {resolve, reject, error: new Error(), method});
@@ -105,8 +120,8 @@ export class FFConnection extends platform.EventEmitter {
     if (this._closed)
       return;
     this._closed = true;
-    this._transport.onmessage = null;
-    this._transport.onclose = null;
+    this._transport.onmessage = undefined;
+    this._transport.onclose = undefined;
     for (const callback of this._callbacks.values())
       callback.reject(rewriteError(callback.error, `Protocol error (${callback.method}): Target closed.`));
     this._callbacks.clear();
@@ -123,7 +138,7 @@ export class FFConnection extends platform.EventEmitter {
 
   async createSession(targetId: string): Promise<FFSession> {
     const {sessionId} = await this.send('Target.attachToTarget', {targetId});
-    return this._sessions.get(sessionId);
+    return this._sessions.get(sessionId)!;
   }
 }
 
@@ -132,7 +147,7 @@ export const FFSessionEvents = {
 };
 
 export class FFSession extends platform.EventEmitter {
-  _connection: FFConnection;
+  _connection: FFConnection | null;
   private _callbacks: Map<number, {resolve: Function, reject: Function, error: Error, method: string}>;
   private _targetType: string;
   private _sessionId: string;
@@ -148,6 +163,12 @@ export class FFSession extends platform.EventEmitter {
     this._connection = connection;
     this._targetType = targetType;
     this._sessionId = sessionId;
+
+    this.on = super.on;
+    this.addListener = super.addListener;
+    this.off = super.removeListener;
+    this.removeListener = super.removeListener;
+    this.once = super.once;
   }
 
   send<T extends keyof Protocol.CommandParameters>(
@@ -164,7 +185,7 @@ export class FFSession extends platform.EventEmitter {
 
   _onMessage(object: { id?: number; method: string; params: object; error: { message: string; data: any; }; result?: any; }) {
     if (object.id && this._callbacks.has(object.id)) {
-      const callback = this._callbacks.get(object.id);
+      const callback = this._callbacks.get(object.id)!;
       this._callbacks.delete(object.id);
       if (object.error)
         callback.reject(createProtocolError(callback.error, callback.method, object));
@@ -176,12 +197,6 @@ export class FFSession extends platform.EventEmitter {
     }
   }
 
-  async detach() {
-    if (!this._connection)
-      throw new Error(`Session already detached. Most likely the ${this._targetType} has been closed.`);
-    await this._connection.send('Target.detachFromTarget',  {sessionId: this._sessionId});
-  }
-
   _onClosed() {
     for (const callback of this._callbacks.values())
       callback.reject(rewriteError(callback.error, `Protocol error (${callback.method}): Target closed.`));
diff --git a/src/firefox/ffExecutionContext.ts b/src/firefox/ffExecutionContext.ts
index 7821fc91ca..f0d03c2d6f 100644
--- a/src/firefox/ffExecutionContext.ts
+++ b/src/firefox/ffExecutionContext.ts
@@ -105,7 +105,7 @@ export class FFExecutionContext implements js.ExecutionContextDelegate {
     checkException(payload.exceptionDetails);
     return context._createHandle(payload.result);
 
-    function rewriteError(error) : never {
+    function rewriteError(error: Error) : never {
       if (error.message.includes('Failed to find execution context with id') || error.message.includes('Execution context was destroyed!'))
         throw new Error('Execution context was destroyed, most likely because of a navigation.');
       throw error;
@@ -146,10 +146,10 @@ export class FFExecutionContext implements js.ExecutionContextDelegate {
     const simpleValue = await this._session.send('Runtime.callFunction', {
       executionContextId: this._executionContextId,
       returnByValue: true,
-      functionDeclaration: (e => e).toString(),
+      functionDeclaration: ((e: any) => e).toString(),
       args: [this._toCallArgument(payload)],
     });
-    return deserializeValue(simpleValue.result);
+    return deserializeValue(simpleValue.result!);
   }
 
   handleToString(handle: js.JSHandle, includeType: boolean): string {
diff --git a/src/firefox/ffInput.ts b/src/firefox/ffInput.ts
index d0f9f96f96..57d645f6fc 100644
--- a/src/firefox/ffInput.ts
+++ b/src/firefox/ffInput.ts
@@ -38,6 +38,7 @@ function toButtonNumber(button: input.Button): number {
     return 1;
   if (button === 'right')
     return 2;
+  return 0;
 }
 
 function toButtonsMask(buttons: Set<input.Button>): number {
diff --git a/src/firefox/ffNetworkManager.ts b/src/firefox/ffNetworkManager.ts
index c0801ab01f..68969eecd8 100644
--- a/src/firefox/ffNetworkManager.ts
+++ b/src/firefox/ffNetworkManager.ts
@@ -21,6 +21,7 @@ import { Page } from '../page';
 import * as network from '../network';
 import * as frames from '../frames';
 import * as platform from '../platform';
+import { Protocol } from './protocol';
 
 export class FFNetworkManager {
   private _session: FFSession;
@@ -46,11 +47,11 @@ export class FFNetworkManager {
     helper.removeEventListeners(this._eventListeners);
   }
 
-  async setRequestInterception(enabled) {
+  async setRequestInterception(enabled: boolean) {
     await this._session.send('Network.setRequestInterception', {enabled});
   }
 
-  _onRequestWillBeSent(event) {
+  _onRequestWillBeSent(event: Protocol.Network.requestWillBeSentPayload) {
     const redirected = event.redirectedFrom ? this._requests.get(event.redirectedFrom) : null;
     const frame = redirected ? redirected.request.frame() : (event.frameId ? this._page._frameManager.frame(event.frameId) : null);
     if (!frame)
@@ -66,11 +67,11 @@ export class FFNetworkManager {
     this._page._frameManager.requestStarted(request.request);
   }
 
-  _onResponseReceived(event) {
+  _onResponseReceived(event: Protocol.Network.responseReceivedPayload) {
     const request = this._requests.get(event.requestId);
     if (!request)
       return;
-    const remoteAddress: network.RemoteAddress = { ip: event.remoteIPAddress, port: event.remotePort };
+    const remoteAddress: network.RemoteAddress = { ip: event.remoteIPAddress || '', port: event.remotePort || 0 };
     const getResponseBody = async () => {
       const response = await this._session.send('Network.getResponseBody', {
         requestId: request._id
@@ -86,11 +87,11 @@ export class FFNetworkManager {
     this._page._frameManager.requestReceivedResponse(response);
   }
 
-  _onRequestFinished(event) {
+  _onRequestFinished(event: Protocol.Network.requestFinishedPayload) {
     const request = this._requests.get(event.requestId);
     if (!request)
       return;
-    const response = request.request.response();
+    const response = request.request.response()!;
     // Keep redirected requests in the map for future reference in redirectChain.
     const isRedirected = response.status() >= 300 && response.status() <= 399;
     if (isRedirected) {
@@ -102,19 +103,20 @@ export class FFNetworkManager {
     this._page._frameManager.requestFinished(request.request);
   }
 
-  _onRequestFailed(event) {
+  _onRequestFailed(event: Protocol.Network.requestFailedPayload) {
     const request = this._requests.get(event.requestId);
     if (!request)
       return;
     this._requests.delete(request._id);
-    if (request.request.response())
-      request.request.response()._requestFinished();
+    const response = request.request.response();
+    if (response)
+      response._requestFinished();
     request.request._setFailureText(event.errorCode);
     this._page._frameManager.requestFailed(request.request, event.errorCode === 'NS_BINDING_ABORTED');
   }
 }
 
-const causeToResourceType = {
+const causeToResourceType: {[key: string]: string} = {
   TYPE_INVALID: 'other',
   TYPE_OTHER: 'other',
   TYPE_SCRIPT: 'script',
@@ -145,7 +147,7 @@ class InterceptableRequest implements network.RequestDelegate {
   _id: string;
   private _session: FFSession;
 
-  constructor(session: FFSession, frame: frames.Frame, redirectChain: network.Request[], payload: any) {
+  constructor(session: FFSession, frame: frames.Frame, redirectChain: network.Request[], payload: Protocol.Network.requestWillBeSentPayload) {
     this._id = payload.requestId;
     this._session = session;
 
diff --git a/src/firefox/ffPage.ts b/src/firefox/ffPage.ts
index eae4e7cc52..67526195b3 100644
--- a/src/firefox/ffPage.ts
+++ b/src/firefox/ffPage.ts
@@ -87,7 +87,8 @@ export class FFPage implements PageDelegate {
     await Promise.all(promises);
   }
 
-  _onExecutionContextCreated({executionContextId, auxData}) {
+  _onExecutionContextCreated(payload: Protocol.Runtime.executionContextCreatedPayload) {
+    const {executionContextId, auxData} = payload;
     const frame = this._page._frameManager.frame(auxData ? auxData.frameId : null);
     if (!frame)
       return;
@@ -98,7 +99,8 @@ export class FFPage implements PageDelegate {
     this._contextIdToContext.set(executionContextId, context);
   }
 
-  _onExecutionContextDestroyed({executionContextId}) {
+  _onExecutionContextDestroyed(payload: Protocol.Runtime.executionContextDestroyedPayload) {
+    const {executionContextId} = payload;
     const context = this._contextIdToContext.get(executionContextId);
     if (!context)
       return;
@@ -110,7 +112,7 @@ export class FFPage implements PageDelegate {
   }
 
   _onNavigationAborted(params: Protocol.Page.navigationAbortedPayload) {
-    const frame = this._page._frameManager.frame(params.frameId);
+    const frame = this._page._frameManager.frame(params.frameId)!;
     for (const watcher of this._page._frameManager._lifecycleWatchers)
       watcher._onAbortedNewDocumentNavigation(frame, params.navigationId, params.errorText);
   }
@@ -131,7 +133,8 @@ export class FFPage implements PageDelegate {
     this._page._frameManager.frameDetached(params.frameId);
   }
 
-  _onEventFired({frameId, name}) {
+  _onEventFired(payload: Protocol.Page.eventFiredPayload) {
+    const {frameId, name} = payload;
     if (name === 'load')
       this._page._frameManager.frameLifecycleEvent(frameId, 'load');
     if (name === 'DOMContentLoaded')
@@ -144,8 +147,9 @@ export class FFPage implements PageDelegate {
     this._page.emit(Events.Page.PageError, error);
   }
 
-  _onConsole({type, args, executionContextId, location}) {
-    const context = this._contextIdToContext.get(executionContextId);
+  _onConsole(payload: Protocol.Runtime.consolePayload) {
+    const {type, args, executionContextId, location} = payload;
+    const context = this._contextIdToContext.get(executionContextId)!;
     this._page._addConsoleMessage(type, args.map(arg => context._createHandle(arg)), location);
   }
 
@@ -160,12 +164,13 @@ export class FFPage implements PageDelegate {
   }
 
   _onBindingCalled(event: Protocol.Page.bindingCalledPayload) {
-    const context = this._contextIdToContext.get(event.executionContextId);
+    const context = this._contextIdToContext.get(event.executionContextId)!;
     this._page._onBindingCalled(event.payload, context);
   }
 
-  async _onFileChooserOpened({executionContextId, element}) {
-    const context = this._contextIdToContext.get(executionContextId);
+  async _onFileChooserOpened(payload: Protocol.Page.fileChooserOpenedPayload) {
+    const {executionContextId, element} = payload;
+    const context = this._contextIdToContext.get(executionContextId)!;
     const handle = context._createHandle(element).asElement()!;
     this._page._onFileChooserOpened(handle);
   }
@@ -184,7 +189,7 @@ export class FFPage implements PageDelegate {
 
   async navigateFrame(frame: frames.Frame, url: string, referer: string | undefined): Promise<frames.GotoResult> {
     const response = await this._session.send('Page.navigate', { url, referer, frameId: frame._id });
-    return { newDocumentId: response.navigationId, isSameDocument: !response.navigationId };
+    return { newDocumentId: response.navigationId || undefined, isSameDocument: !response.navigationId };
   }
 
   needsLifecycleResetOnSetContent(): boolean {
@@ -292,7 +297,7 @@ export class FFPage implements PageDelegate {
   async getContentFrame(handle: dom.ElementHandle): Promise<frames.Frame | null> {
     const { frameId } = await this._session.send('Page.contentFrame', {
       frameId: handle._context.frame._id,
-      objectId: toRemoteObject(handle).objectId,
+      objectId: toRemoteObject(handle).objectId!,
     });
     if (!frameId)
       return null;
@@ -329,7 +334,7 @@ export class FFPage implements PageDelegate {
   async getContentQuads(handle: dom.ElementHandle): Promise<types.Quad[] | null> {
     const result = await this._session.send('Page.getContentQuads', {
       frameId: handle._context.frame._id,
-      objectId: toRemoteObject(handle).objectId,
+      objectId: toRemoteObject(handle).objectId!,
     }).catch(debugError);
     if (!result)
       return null;
@@ -340,7 +345,7 @@ export class FFPage implements PageDelegate {
     return this._page.evaluate(() => ({ width: innerWidth, height: innerHeight }));
   }
 
-  async setInputFiles(handle: dom.ElementHandle, files: types.FilePayload[]): Promise<void> {
+  async setInputFiles(handle: dom.ElementHandle<HTMLInputElement>, files: types.FilePayload[]): Promise<void> {
     await handle.evaluate(dom.setFileInputFunction, files);
   }
 
diff --git a/src/helper.ts b/src/helper.ts
index 77e93fea57..8644653c3f 100644
--- a/src/helper.ts
+++ b/src/helper.ts
@@ -69,7 +69,7 @@ class Helper {
         const value = target[key];
         if (typeof key === 'string' && key.startsWith('_') || typeof value !== 'function')
           return value;
-        return function(...args: any) {
+        return function(this: any, ...args: any) {
           if (args.length)
             log(`${className}.${key} %o`, args);
           else
diff --git a/src/injected/tsconfig.json b/src/injected/tsconfig.json
deleted file mode 100644
index 9b96b484ca..0000000000
--- a/src/injected/tsconfig.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "compilerOptions": {
-    "strict": true
-  },
-  "extends": "../../tsconfig.json"
-}
diff --git a/src/screenshotter.ts b/src/screenshotter.ts
index a2a0a950ec..3cfe046099 100644
--- a/src/screenshotter.ts
+++ b/src/screenshotter.ts
@@ -108,7 +108,7 @@ export class Screenshotter {
       const viewport = this._page.viewport();
       if (!this._page._delegate.canScreenshotOutsideViewport()) {
         if (!viewport) {
-          viewportSize = await this._page.evaluate(() => {
+          const maybeViewportSize = await this._page.evaluate(() => {
             if (!document.body || !document.documentElement)
               return;
             return {
@@ -116,8 +116,9 @@ export class Screenshotter {
               height: Math.max(document.body.offsetHeight, document.documentElement.offsetHeight),
             };
           });
-          if (!viewportSize)
+          if (!maybeViewportSize)
             throw new Error(kScreenshotDuringNavigationError);
+          viewportSize = maybeViewportSize!;
         } else {
           viewportSize = viewport;
         }
@@ -137,7 +138,7 @@ export class Screenshotter {
       if (!overridenViewport)
         rewrittenOptions.clip = boundingBox;
 
-      const result = await this._screenshot(format, rewrittenOptions, overridenViewport || viewport);
+      const result = await this._screenshot(format, rewrittenOptions, (overridenViewport || viewport)!);
 
       if (overridenViewport) {
         if (viewport)
diff --git a/src/server/tsconfig.json b/src/server/tsconfig.json
deleted file mode 100644
index 9b96b484ca..0000000000
--- a/src/server/tsconfig.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "compilerOptions": {
-    "strict": true
-  },
-  "extends": "../../tsconfig.json"
-}
diff --git a/src/webkit/tsconfig.json b/src/webkit/tsconfig.json
deleted file mode 100644
index 9b96b484ca..0000000000
--- a/src/webkit/tsconfig.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "compilerOptions": {
-    "strict": true
-  },
-  "extends": "../../tsconfig.json"
-}
diff --git a/src/webkit/wkAccessibility.ts b/src/webkit/wkAccessibility.ts
index d115233420..d957f4b988 100644
--- a/src/webkit/wkAccessibility.ts
+++ b/src/webkit/wkAccessibility.ts
@@ -101,12 +101,8 @@ class WKAXNode implements accessibility.AXNode {
         role: this._payload.role,
         name: this._payload.name || '',
       };
-      type AXPropertyOfType<Type> = {
-        [Key in keyof Protocol.Page.AXNode]:
-            Protocol.Page.AXNode[Key] extends Type ? Key : never
-      }[keyof Protocol.Page.AXNode];
 
-      const userStringProperties: AXPropertyOfType<string>[] = [
+      const userStringProperties: string[] = [
         'value',
         'description',
         'keyshortcuts',
@@ -116,10 +112,10 @@ class WKAXNode implements accessibility.AXNode {
       for (const userStringProperty of userStringProperties) {
         if (!(userStringProperty in this._payload))
           continue;
-        node[userStringProperty] = this._payload[userStringProperty];
+        (node as any)[userStringProperty] = (this._payload as any)[userStringProperty];
       }
 
-      const booleanProperties: AXPropertyOfType<boolean>[] = [
+      const booleanProperties: string[] = [
         'disabled',
         'expanded',
         'focused',
@@ -135,10 +131,10 @@ class WKAXNode implements accessibility.AXNode {
         // not whether focus is specifically on the root node.
         if (booleanProperty === 'focused' && (this._payload.role === 'WebArea' || this._payload.role === 'ScrollArea'))
           continue;
-        const value = this._payload[booleanProperty];
+        const value = (this._payload as any)[booleanProperty];
         if (!value)
           continue;
-        node[booleanProperty] = value;
+        (node as any)[booleanProperty] = value;
       }
 
       const tristateProperties: ('checked'|'pressed')[] = [
@@ -151,7 +147,7 @@ class WKAXNode implements accessibility.AXNode {
         const value = this._payload[tristateProperty];
         node[tristateProperty] = value === 'mixed' ? 'mixed' : value === 'true' ? true : false;
       }
-      const numericalProperties: AXPropertyOfType<number>[] = [
+      const numericalProperties: string[] = [
         'level',
         'valuemax',
         'valuemin',
@@ -159,18 +155,18 @@ class WKAXNode implements accessibility.AXNode {
       for (const numericalProperty of numericalProperties) {
         if (!(numericalProperty in this._payload))
           continue;
-        node[numericalProperty] = this._payload[numericalProperty];
+        (node as any)[numericalProperty] = (this._payload as any)[numericalProperty];
       }
-      const tokenProperties: AXPropertyOfType<string>[] = [
+      const tokenProperties: string[] = [
         'autocomplete',
         'haspopup',
         'invalid',
       ];
       for (const tokenProperty of tokenProperties) {
-        const value = this._payload[tokenProperty];
+        const value = (this._payload as any)[tokenProperty];
         if (!value || value === 'false')
           continue;
-        node[tokenProperty] = value;
+        (node as any)[tokenProperty] = value;
       }
 
       const orientationIsApplicable = new Set([
diff --git a/tsconfig.json b/tsconfig.json
index 6bf59db7ef..43224d7e28 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,7 +6,7 @@
     "sourceMap": true,
     "rootDir": "./src",
     "outDir": "./lib",
-    "strictBindCallApply": true,
+    "strict": true,
     "declaration": true
   },
   "compileOnSave": true,
diff --git a/utils/protocol-types-generator/index.js b/utils/protocol-types-generator/index.js
index e935450bb6..2a43a88562 100644
--- a/utils/protocol-types-generator/index.js
+++ b/utils/protocol-types-generator/index.js
@@ -9,7 +9,7 @@ async function generateChromiunProtocol(revision) {
   const outputPath = path.join(__dirname, '..', '..', 'src', 'chromium', 'protocol.ts');
   if (revision.local && fs.existsSync(outputPath))
     return;
-  const playwright = await require('../../chromium');
+  const playwright = await require('../../index').chromium;
   const browserServer = await playwright.launchServer({executablePath: revision.executablePath});
   const origin = browserServer.wsEndpoint().match(/ws:\/\/([0-9A-Za-z:\.]*)\//)[1];
   const page = await (await browserServer.connect()).defaultContext().newPage();
@@ -211,7 +211,7 @@ function firefoxTypeToString(type, indent='    ') {
   if (type['$type'] === 'array')
     return firefoxTypeToString(type['$items'], indent) + '[]';
   if (type['$type'] === 'enum')
-    return type['$values'].map(v => JSON.stringify(v)).join('|');
+    return '(' + type['$values'].map(v => JSON.stringify(v)).join('|') + ')';
   return type['$type'];
 }