--- a/browser/base/content/test/performance/browser_startup.js
+++ b/browser/base/content/test/performance/browser_startup.js
@@ -61,16 +61,18 @@ const startupPhases = {
   "before first paint": {blacklist: {
     components: new Set([
       "UnifiedComplete.js",
       "nsSearchService.js",
     ]),
     modules: new Set([
       "chrome://webcompat-reporter/content/TabListener.jsm",
       "chrome://webcompat-reporter/content/WebCompatReporter.jsm",
+      "chrome://webcompat/content/data/ua_overrides.jsm",
+      "chrome://webcompat/content/lib/ua_overrider.jsm",
       "resource:///modules/AboutNewTab.jsm",
       "resource:///modules/BrowserUITelemetry.jsm",
       "resource:///modules/BrowserUsageTelemetry.jsm",
       "resource:///modules/ContentCrashHandlers.jsm",
       "resource:///modules/DirectoryLinksProvider.jsm",
       "resource://gre/modules/NewTabUtils.jsm",
       "resource://gre/modules/PageThumbs.jsm",
       "resource://gre/modules/Promise.jsm", // imported by devtools during _delayedStartup