--- a/toolkit/components/search/nsSearchService.js
+++ b/toolkit/components/search/nsSearchService.js
@@ -406,17 +406,22 @@ loadListener.prototype = {
 // Hacky method that tries to determine if this user is in a US geography, and
 // using an en-US build.
 function getIsUS() {
   let geoSpecificDefaults = false;
   try {
     geoSpecificDefaults = Services.prefs.getBoolPref("browser.search.geoSpecificDefaults");
   } catch(e) {}
 
-  if (!geoSpecificDefaults) {
+  let distroID;
+  try {
+    distroID = Services.prefs.getCharPref("distribution.id");
+  } catch (e) {}
+
+  if (!geoSpecificDefaults || distroID) {
     return false;
   }
 
   // If we've set the pref before, just return that result.
   let cachePref = "browser.search.isUS";
   try {
     return Services.prefs.getBoolPref(cachePref);
   } catch(e) {}