--- a/testing/marionette/client/marionette_driver/geckoinstance.py
+++ b/testing/marionette/client/marionette_driver/geckoinstance.py
@@ -32,17 +32,18 @@ class GeckoInstance(object):
         "dom.ipc.reportProcessHangs": False,
         # Only install add-ons from the profile and the application scope
         # Also ensure that those are not getting disabled.
         # see: https://developer.mozilla.org/en/Installing_extensions
         "extensions.enabledScopes": 5,
         "extensions.autoDisableScopes": 10,
         "focusmanager.testmode": True,
         "marionette.defaultPrefs.enabled": True,
-        "startup.homepage_welcome_url": "about:blank",
+        "startup.homepage_welcome_url": "",
+        "startup.homepage_welcome_url.additional": "",
         "toolkit.telemetry.enabled": False,
         # Until Bug 1238095 is fixed, we have to enable CPOWs in order
         # for Marionette tests to work properly.
         "dom.ipc.cpows.forbid-unsafe-from-browser": False,
     }
 
     def __init__(self, host, port, bin, profile=None, addons=None,
                  app_args=None, symbols_path=None, gecko_log=None, prefs=None,
@@ -293,30 +294,32 @@ class B2GDesktopInstance(GeckoInstance):
         self.app_args += ['-chrome', 'chrome://b2g/content/shell.html']
 
 
 class DesktopInstance(GeckoInstance):
     desktop_prefs = {
         'app.update.auto': False,
         'app.update.enabled': False,
         'browser.dom.window.dump.enabled': True,
+        'browser.firstrun-content.dismissed': True,
         # Bug 1145668 - Has to be reverted to about:blank once Marionette
         # can correctly handle error pages
         'browser.newtab.url': 'about:newtab',
         'browser.newtabpage.enabled': False,
         'browser.reader.detectedFirstArticle': True,
-        'browser.safebrowsing.phishing.enabled': False,
+        'browser.safebrowsing.blockedURIs.enabled': False,
         'browser.safebrowsing.forbiddenURIs.enabled': False,
         'browser.safebrowsing.malware.enabled': False,
-        'browser.safebrowsing.blockedURIs.enabled': False,
+        'browser.safebrowsing.phishing.enabled': False,
         'browser.search.update': False,
         'browser.tabs.animate': False,
         'browser.tabs.warnOnClose': False,
         'browser.tabs.warnOnOpen': False,
         'browser.uitour.enabled': False,
+        'browser.usedOnWindows10.introURL': '',
         'extensions.getAddons.cache.enabled': False,
         'extensions.installDistroAddons': False,
         'extensions.showMismatchUI': False,
         'extensions.update.enabled': False,
         'extensions.update.notifyUser': False,
         'geo.provider.testing': True,
         'javascript.options.showInConsole': True,
         'privacy.trackingprotection.enabled': False,