--- a/b2g/dev/confvars.sh
+++ b/b2g/dev/confvars.sh
@@ -4,8 +4,9 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 MOZ_B2G=1
 MOZ_MULET=1
 
 . ${srcdir}/browser/confvars.sh
 
 MOZ_BUNDLED_FONTS=1
+MOZ_UA_OS_AGNOSTIC=1

--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -321,17 +321,17 @@ nsHttpHandler::Init()
     if (NS_FAILED(rv)) return rv;
 
     rv = InitConnectionMgr();
     if (NS_FAILED(rv)) return rv;
 
     mSchedulingContextService =
         do_GetService("@mozilla.org/network/scheduling-context-service;1");
 
-#ifdef ANDROID
+#if defined(ANDROID) || defined(MOZ_MULET)
     mProductSub.AssignLiteral(MOZILLA_UAVERSION);
 #else
     mProductSub.AssignLiteral("20100101");
 #endif
 
 #if DEBUG
     // dump user agent prefs
     LOG(("> legacy-app-name = %s\n", mLegacyAppName.get()));
@@ -772,29 +772,29 @@ nsHttpHandler::InitUserAgentComponents()
         if (NS_SUCCEEDED(rv) && isTV) {
             mCompatDevice.AssignLiteral("TV");
         } else {
             mCompatDevice.AssignLiteral("Mobile");
         }
     }
 #endif // ANDROID
 
-#ifdef FXOS_SIMULATOR
+#ifdef MOZ_MULET
     {
         // Add the `Mobile` or `Tablet` or `TV` token when running in the b2g
         // desktop simulator via preference.
         nsCString deviceType;
         nsresult rv = Preferences::GetCString("devtools.useragent.device_type", &deviceType);
         if (NS_SUCCEEDED(rv)) {
             mCompatDevice.Assign(deviceType);
         } else {
             mCompatDevice.AssignLiteral("Mobile");
         }
     }
-#endif // FXOS_SIMULATOR
+#endif // MOZ_MULET
 
 #if defined(MOZ_WIDGET_GONK)
     // Device model identifier should be a simple token, which can be composed
     // of letters, numbers, hyphen ("-") and dot (".").
     // Any other characters means the identifier is invalid and ignored.
     nsCString deviceId;
     rv = Preferences::GetCString("general.useragent.device_id", &deviceId);
     if (NS_SUCCEEDED(rv)) {