diff --git a/.npmignore b/.npmignore
index 39b253454b..f333d1d5f8 100644
--- a/.npmignore
+++ b/.npmignore
@@ -15,6 +15,7 @@ src
 node_modules
 .local-chromium
 .local-browser
+.local-webkit
 .dev_profile*
 .DS_Store
 *.swp
@@ -44,4 +45,4 @@ tsconfig.json
 /index.d.ts
 
 # install.js only does stuff for development
-/install.js
\ No newline at end of file
+/install.js
diff --git a/src/chromium/FrameManager.ts b/src/chromium/FrameManager.ts
index ebfe4014af..68fcb937f8 100644
--- a/src/chromium/FrameManager.ts
+++ b/src/chromium/FrameManager.ts
@@ -16,17 +16,17 @@
  */
 
 import { EventEmitter } from 'events';
+import * as frames from '../frames';
 import { assert, debugError } from '../helper';
+import * as js from '../javascript';
 import { TimeoutSettings } from '../TimeoutSettings';
 import { CDPSession } from './Connection';
-import { EVALUATION_SCRIPT_URL, ExecutionContextDelegate, ExecutionContext, JSHandle, toRemoteObject } from './ExecutionContext';
-import * as frames from '../frames';
-import * as js from '../javascript';
+import { EVALUATION_SCRIPT_URL, ExecutionContext, ExecutionContextDelegate, toRemoteObject } from './ExecutionContext';
+import { ElementHandle } from './JSHandle';
 import { LifecycleWatcher } from './LifecycleWatcher';
 import { NetworkManager, Response } from './NetworkManager';
 import { Page } from './Page';
 import { Protocol } from './protocol';
-import { ElementHandle, createJSHandle } from './JSHandle';
 
 const UTILITY_WORLD_NAME = '__playwright_utility_world__';
 
diff --git a/src/firefox/FrameManager.ts b/src/firefox/FrameManager.ts
index da2c6e51c8..ab46a3f2a0 100644
--- a/src/firefox/FrameManager.ts
+++ b/src/firefox/FrameManager.ts
@@ -15,17 +15,17 @@
  * limitations under the License.
  */
 
-import { JugglerSession } from './Connection';
-import { Page } from './Page';
-import {RegisteredListener, helper, assert} from '../helper';
-import {TimeoutError} from '../Errors';
-import {EventEmitter} from 'events';
-import { JSHandle, ExecutionContext, ExecutionContextDelegate } from './ExecutionContext';
-import {NavigationWatchdog, NextNavigationWatchdog} from './NavigationWatchdog';
-import { ElementHandle } from './JSHandle';
-import { TimeoutSettings } from '../TimeoutSettings';
+import { EventEmitter } from 'events';
+import { TimeoutError } from '../Errors';
 import * as frames from '../frames';
+import { assert, helper, RegisteredListener } from '../helper';
 import * as js from '../javascript';
+import { TimeoutSettings } from '../TimeoutSettings';
+import { JugglerSession } from './Connection';
+import { ExecutionContext, ExecutionContextDelegate } from './ExecutionContext';
+import { ElementHandle } from './JSHandle';
+import { NavigationWatchdog, NextNavigationWatchdog } from './NavigationWatchdog';
+import { Page } from './Page';
 
 export const FrameManagerEvents = {
   FrameNavigated: Symbol('FrameManagerEvents.FrameNavigated'),
diff --git a/src/webkit/ExecutionContext.ts b/src/webkit/ExecutionContext.ts
index 31ad9cc403..09fa3f5015 100644
--- a/src/webkit/ExecutionContext.ts
+++ b/src/webkit/ExecutionContext.ts
@@ -31,7 +31,7 @@ export type JSHandle = js.JSHandle<ElementHandle>;
 export class ExecutionContextDelegate implements js.ExecutionContextDelegate<ElementHandle> {
   private _globalObjectId?: string;
   _session: TargetSession;
-  private _contextId: number;
+  _contextId: number;
   private _contextDestroyedCallback: () => void;
   private _executionContextDestroyedPromise: Promise<unknown>;
 
@@ -157,7 +157,7 @@ export class ExecutionContextDelegate implements js.ExecutionContextDelegate<Ele
         functionDeclaration: functionText + '\n' + suffix + '\n',
         // TODO(yurys): support executionContextId in WebKit
         objectId: thisObjectId,
-        arguments: serializableArgs.map(convertArgument.bind(this)),
+        arguments: serializableArgs.map((arg: any) => this._convertArgument(arg)),
         returnByValue: false,
         emulateUserGesture: true
       });
@@ -217,21 +217,6 @@ export class ExecutionContextDelegate implements js.ExecutionContextDelegate<Ele
       return valueFromRemoteObject(response.result);
     }).catch(rewriteError);
 
-    function convertArgument(this: ExecutionContext, arg: JSHandle | any) : Protocol.Runtime.CallArgument{
-      const objectHandle = arg && (arg instanceof js.JSHandle) ? arg : null;
-      if (objectHandle) {
-        if (objectHandle._context !== this)
-          throw new Error('JSHandles can be evaluated only in the context they were created!');
-        if (objectHandle._disposed)
-          throw new Error('JSHandle is disposed!');
-        const remoteObject = toRemoteObject(arg);
-        if (!remoteObject.objectId)
-          return { value: valueFromRemoteObject(remoteObject) };
-        return { objectId: remoteObject.objectId };
-      }
-      return { value: arg };
-    }
-
     function unserializableToString(arg) {
       if (Object.is(arg, -0))
         return '-0';
@@ -332,6 +317,22 @@ export class ExecutionContextDelegate implements js.ExecutionContextDelegate<Ele
     }
     return 'JSHandle:' + valueFromRemoteObject(object);
   }
+
+  private _convertArgument(arg: JSHandle | any) : Protocol.Runtime.CallArgument {
+    const objectHandle = arg && (arg instanceof js.JSHandle) ? arg : null;
+    if (objectHandle) {
+      if (objectHandle._context._delegate !== this)
+        throw new Error('JSHandles can be evaluated only in the context they were created!');
+      if (objectHandle._disposed)
+        throw new Error('JSHandle is disposed!');
+      const remoteObject = toRemoteObject(arg);
+      if (!remoteObject.objectId)
+        return { value: valueFromRemoteObject(remoteObject) };
+      return { objectId: remoteObject.objectId };
+    }
+    return { value: arg };
+  }
+
 }
 
 const remoteObjectSymbol = Symbol('RemoteObject');
diff --git a/src/webkit/FrameManager.ts b/src/webkit/FrameManager.ts
index a6fa88e9b0..9bdb425984 100644
--- a/src/webkit/FrameManager.ts
+++ b/src/webkit/FrameManager.ts
@@ -17,17 +17,17 @@
 
 import * as EventEmitter from 'events';
 import { TimeoutError } from '../Errors';
-import { Events } from './events';
+import * as frames from '../frames';
 import { assert, debugError, helper, RegisteredListener } from '../helper';
+import * as js from '../javascript';
 import { TimeoutSettings } from '../TimeoutSettings';
 import { TargetSession } from './Connection';
-import { JSHandle, ExecutionContext, ExecutionContextDelegate } from './ExecutionContext';
+import { Events } from './events';
+import { ExecutionContext, ExecutionContextDelegate } from './ExecutionContext';
 import { ElementHandle } from './JSHandle';
 import { NetworkManager, NetworkManagerEvents, Request, Response } from './NetworkManager';
 import { Page } from './Page';
 import { Protocol } from './protocol';
-import * as frames from '../frames';
-import * as js from '../javascript';
 
 export const FrameManagerEvents = {
   FrameNavigatedWithinDocument: Symbol('FrameNavigatedWithinDocument'),
@@ -178,6 +178,7 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate<E
         const data = this._frameData(frame);
         this._frames.delete(data.id);
         data.id = framePayload.id;
+        this._frames.set(data.id, frame);
       }
     } else if (isMainFrame) {
       // Initial frame navigation.
@@ -199,7 +200,9 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate<E
     frame._navigated(framePayload.url, framePayload.name);
     for (const context of this._contextIdToContext.values()) {
       if (context.frame() === frame) {
-        (context._delegate as ExecutionContextDelegate)._dispose();
+        const delegate = context._delegate as ExecutionContextDelegate;
+        delegate._dispose();
+        this._contextIdToContext.delete(delegate._contextId);
         frame._contextDestroyed(context);
       }
     }
@@ -223,6 +226,8 @@ export class FrameManager extends EventEmitter implements frames.FrameDelegate<E
   }
 
   _onExecutionContextCreated(contextPayload : Protocol.Runtime.ExecutionContextDescription) {
+    if (this._contextIdToContext.has(contextPayload.id))
+      return;
     if (!contextPayload.isPageContext)
       return;
     const frameId = contextPayload.frameId;