diff --git a/experimental/puppeteer-firefox/lib/Page.js b/experimental/puppeteer-firefox/lib/Page.js
index 91a35b93..0ff24682 100644
--- a/experimental/puppeteer-firefox/lib/Page.js
+++ b/experimental/puppeteer-firefox/lib/Page.js
@@ -88,6 +88,23 @@ class Page extends EventEmitter {
     this._viewport = null;
   }
 
+  /**
+   * @param {string} userAgent
+   */
+  async setUserAgent(userAgent) {
+    await this._session.send('Page.setUserAgent', {userAgent});
+  }
+
+  /**
+   * @param {{viewport: !Puppeteer.Viewport, userAgent: string}} options
+   */
+  async emulate(options) {
+    await Promise.all([
+      this.setViewport(options.viewport),
+      this.setUserAgent(options.userAgent),
+    ]);
+  }
+
   /**
    * @return {BrowserContext}
    */
diff --git a/experimental/puppeteer-firefox/package.json b/experimental/puppeteer-firefox/package.json
index a45db348..00afacc6 100644
--- a/experimental/puppeteer-firefox/package.json
+++ b/experimental/puppeteer-firefox/package.json
@@ -9,7 +9,7 @@
     "node": ">=8.9.4"
   },
   "puppeteer": {
-    "firefox_revision": "9702d3d2dd86550e385fadec66eb28a5ff2b1322"
+    "firefox_revision": "ba500612786aac157fa44e6b4d04c852f51ea35c"
   },
   "scripts": {
     "install": "node install.js",
diff --git a/test/emulation.spec.js b/test/emulation.spec.js
index 71b4704a..a2ce575f 100644
--- a/test/emulation.spec.js
+++ b/test/emulation.spec.js
@@ -82,12 +82,12 @@ module.exports.addTests = function({testRunner, expect, product}) {
     });
   });
 
-  describe_fails_ffox('Page.emulate', function() {
+  describe('Page.emulate', function() {
     it('should work', async({page, server}) => {
       await page.goto(server.PREFIX + '/mobile.html');
       await page.emulate(iPhone);
       expect(await page.evaluate(() => window.innerWidth)).toBe(375);
-      expect(await page.evaluate(() => navigator.userAgent)).toContain('Safari');
+      expect(await page.evaluate(() => navigator.userAgent)).toContain('iPhone');
     });
     it('should support clicking', async({page, server}) => {
       await page.emulate(iPhone);
diff --git a/test/page.spec.js b/test/page.spec.js
index 59717612..114af156 100644
--- a/test/page.spec.js
+++ b/test/page.spec.js
@@ -628,21 +628,30 @@ module.exports.addTests = function({testRunner, expect, headless, Errors, Device
     });
   });
 
-  describe_fails_ffox('Page.setUserAgent', function() {
+  describe('Page.setUserAgent', function() {
     it('should work', async({page, server}) => {
       expect(await page.evaluate(() => navigator.userAgent)).toContain('Mozilla');
-      page.setUserAgent('foobar');
+      await page.setUserAgent('foobar');
       const [request] = await Promise.all([
         server.waitForRequest('/empty.html'),
         page.goto(server.EMPTY_PAGE),
       ]);
       expect(request.headers['user-agent']).toBe('foobar');
     });
+    it('should work for subframes', async({page, server}) => {
+      expect(await page.evaluate(() => navigator.userAgent)).toContain('Mozilla');
+      await page.setUserAgent('foobar');
+      const [request] = await Promise.all([
+        server.waitForRequest('/empty.html'),
+        utils.attachFrame(page, 'frame1', server.EMPTY_PAGE),
+      ]);
+      expect(request.headers['user-agent']).toBe('foobar');
+    });
     it('should emulate device user-agent', async({page, server}) => {
       await page.goto(server.PREFIX + '/mobile.html');
-      expect(await page.evaluate(() => navigator.userAgent)).toContain('Chrome');
+      expect(await page.evaluate(() => navigator.userAgent)).not.toContain('iPhone');
       await page.setUserAgent(iPhone.userAgent);
-      expect(await page.evaluate(() => navigator.userAgent)).toContain('Safari');
+      expect(await page.evaluate(() => navigator.userAgent)).toContain('iPhone');
     });
   });