diff --git 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
index c70a2f8c9826..6bdfd39066c6 100644
--- 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
@@ -32,6 +32,7 @@ class TestSafeBrowsingInitialDownload(FirefoxTestCase):
     }
 
     prefs_safebrowsing = {
+        'browser.safebrowsing.debug': True,
         'browser.safebrowsing.blockedURIs.enabled': True,
         'browser.safebrowsing.downloads.enabled': True,
         'browser.safebrowsing.phishing.enabled': True,