--- a/testing/firefox-ui/tests/functional/security/test_safe_browsing_initial_download.py
+++ b/testing/firefox-ui/tests/functional/security/test_safe_browsing_initial_download.py
@@ -1,13 +1,14 @@
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
+import time
 
 from firefox_puppeteer import PuppeteerMixin
 from marionette_driver import Wait
 from marionette_harness import MarionetteTestCase
 
 
 class TestSafeBrowsingInitialDownload(PuppeteerMixin, MarionetteTestCase):
 
@@ -96,16 +97,19 @@ class TestSafeBrowsingInitialDownload(Pu
         def check_downloaded(_):
             return reduce(lambda state, pref: state and int(self.marionette.get_pref(pref)) != 1,
                           self.prefs_provider_update_time.keys(), True)
 
         try:
             Wait(self.marionette, timeout=90).until(
                 check_downloaded, message='Not all safebrowsing files have been downloaded')
         finally:
+            # Wait for slow disks to finish writing the tables to disk
+            time.sleep(30)
+
             files_on_disk_toplevel = os.listdir(self.safebrowsing_path)
             for f in self.safebrowsing_v2_files:
                 self.assertIn(f, files_on_disk_toplevel)
 
             if len(self.safebrowsing_v4_files) > 0:
                 files_on_disk_google4 = os.listdir(os.path.join(self.safebrowsing_path, 'google4'))
                 for f in self.safebrowsing_v4_files:
                     self.assertIn(f, files_on_disk_google4)