diff --git a/docs/api.md b/docs/api.md
index 9b5c9fc5bec..460bab04f2e 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -76,6 +76,7 @@
     + [tracing.stop()](#tracingstop)
   * [class: Dialog](#class-dialog)
     + [dialog.accept([promptText])](#dialogacceptprompttext)
+    + [dialog.defaultValue()](#dialogdefaultvalue)
     + [dialog.dismiss()](#dialogdismiss)
     + [dialog.message()](#dialogmessage)
     + [dialog.type](#dialogtype)
@@ -901,6 +902,9 @@ browser.newPage().then(async page => {
 - `promptText` <[string]> A text to enter in prompt. Does not cause any effects if the dialog's `type` is not prompt.
 - returns: <[Promise]> Promise which resolves when the dialog has being accepted.
 
+#### dialog.defaultValue()
+- returns: <[string]> If dialog is prompt, returns default prompt value. Otherwise, returns empty string.
+
 #### dialog.dismiss()
 - returns: <[Promise]> Promise which resolves when the dialog has being dismissed.
 
diff --git a/lib/Dialog.js b/lib/Dialog.js
index 0ad4b58c6cf..33cdb1fd95c 100644
--- a/lib/Dialog.js
+++ b/lib/Dialog.js
@@ -21,12 +21,14 @@ class Dialog {
    * @param {!Session} client
    * @param {!Dialog.Type} type
    * @param {string} message
+   * @param {(string|undefined)} defaultValue
    */
-  constructor(client, type, message) {
+  constructor(client, type, message, defaultValue) {
     this._client = client;
     this.type = type;
     this._message = message;
     this._handled = false;
+    this._defaultValue = defaultValue || '';
   }
 
   /**
@@ -36,6 +38,13 @@ class Dialog {
     return this._message;
   }
 
+  /**
+   * @return {string}
+   */
+  defaultValue() {
+    return this._defaultValue;
+  }
+
   /**
    * @param {string=} promptText
    * @return {!Promise}
diff --git a/lib/Page.js b/lib/Page.js
index 75b58ebdd13..dad2e4ed536 100644
--- a/lib/Page.js
+++ b/lib/Page.js
@@ -237,7 +237,7 @@ class Page extends EventEmitter {
     else if (event.type === 'beforeunload')
       dialogType = Dialog.Type.BeforeUnload;
     console.assert(dialogType, 'Unknown javascript dialog type: ' + event.type);
-    let dialog = new Dialog(this._client, dialogType, event.message);
+    let dialog = new Dialog(this._client, dialogType, event.message, event.defaultPrompt);
     this.emit(Page.Events.Dialog, dialog);
   }
 
diff --git a/phantom_shim/WebPage.js b/phantom_shim/WebPage.js
index 596cfa54b60..4a87c28fcfa 100644
--- a/phantom_shim/WebPage.js
+++ b/phantom_shim/WebPage.js
@@ -58,6 +58,7 @@ class WebPage {
 
     this._onResourceRequestedCallback = undefined;
     this._onConfirmCallback = undefined;
+    this._onPromptCallback = undefined;
     this._onAlertCallback = undefined;
     this._onError = noop;
 
@@ -351,6 +352,22 @@ class WebPage {
     this._onConfirmCallback = handler;
   }
 
+  /**
+   * @return {(function()|undefined)}
+   */
+  get onPrompt() {
+    return this._onPromptCallback;
+  }
+
+  /**
+   * @param {function()} handler
+   */
+  set onPrompt(handler) {
+    if (typeof handler !== 'function')
+      handler = undefined;
+    this._onPromptCallback = handler;
+  }
+
   /**
    * @return {(function()|undefined)}
    */
@@ -377,6 +394,9 @@ class WebPage {
     } else if (dialog.type === 'confirm' && this._onConfirmCallback) {
       let result = this._onConfirmCallback.call(null, dialog.message());
       await(result ? dialog.accept() : dialog.dismiss());
+    } else if (dialog.type === 'prompt' && this._onPromptCallback) {
+      let result = this._onPromptCallback.call(null, dialog.message(), dialog.defaultValue());
+      await(result ? dialog.accept(result) : dialog.dismiss());
     }
   }
 
diff --git a/test/test.js b/test/test.js
index 2e933e8b2dc..635081ddeb4 100644
--- a/test/test.js
+++ b/test/test.js
@@ -818,6 +818,7 @@ describe('Page', function() {
     it('should fire', SX(async function() {
       page.on('dialog', dialog => {
         expect(dialog.type).toBe('alert');
+        expect(dialog.defaultValue()).toBe('');
         expect(dialog.message()).toBe('yo');
         dialog.accept();
       });
@@ -826,10 +827,11 @@ describe('Page', function() {
     it('should allow accepting prompts', SX(async function() {
       page.on('dialog', dialog => {
         expect(dialog.type).toBe('prompt');
+        expect(dialog.defaultValue()).toBe('yes.');
         expect(dialog.message()).toBe('question?');
         dialog.accept('answer!');
       });
-      let result = await page.evaluate(() => prompt('question?'));
+      let result = await page.evaluate(() => prompt('question?', 'yes.'));
       expect(result).toBe('answer!');
     }));
     it('should dismiss the prompt', SX(async function() {
diff --git a/third_party/phantomjs/test/module/webpage/prompt.js b/third_party/phantomjs/test/module/webpage/prompt.js
index 2826acf3cd2..d1f099e4ada 100644
--- a/third_party/phantomjs/test/module/webpage/prompt.js
+++ b/third_party/phantomjs/test/module/webpage/prompt.js
@@ -1,4 +1,3 @@
-//! unsupported
 test(function () {
     var page = require('webpage').create();