diff --git a/mobile/app/Makefile.in b/mobile/app/Makefile.in
index 92dfa6f63160..ace34ad00830 100644
--- a/mobile/app/Makefile.in
+++ b/mobile/app/Makefile.in
@@ -108,8 +108,6 @@ DEFINES += -DGRE_MILESTONE=$(GRE_MILESTONE) \
            -DAPP_BUILDID=$(APP_BUILDID) \
            -DAPP_NAME=$(MOZ_APP_NAME) \
            -DAPP_VERSION=$(MOZ_APP_VERSION) \
-           -DAPP_UA_NAME_EXTRA=$(MOZ_APP_UA_EXTRA) \
-           -DAPP_VERSION_EXTRA=$(FIREFOX_VERSION) \
            -DMOZ_UPDATER=$(MOZ_UPDATER) \
            $(NULL)
 
diff --git a/mobile/app/mobile.js b/mobile/app/mobile.js
index 5f1d4d88b6aa..5b09388ea336 100644
--- a/mobile/app/mobile.js
+++ b/mobile/app/mobile.js
@@ -37,7 +37,7 @@
 #filter substitution
 
 pref("toolkit.defaultChromeURI", "chrome://browser/content/browser.xul");
-pref("general.useragent.extra.mobile", "@APP_UA_NAME_EXTRA@/@APP_VERSION_EXTRA@ Fennec/@APP_VERSION@");
+pref("general.useragent.compatMode.firefox", true);
 pref("browser.chromeURL", "chrome://browser/content/");
 
 pref("browser.tabs.warnOnClose", true);
diff --git a/mobile/branding/nightly/configure.sh b/mobile/branding/nightly/configure.sh
index e7ab1afc04ee..dcc4f4a76ef8 100644
--- a/mobile/branding/nightly/configure.sh
+++ b/mobile/branding/nightly/configure.sh
@@ -1,2 +1 @@
 MOZ_APP_DISPLAYNAME=Fennec
-MOZ_APP_UA_EXTRA=Namoroka
diff --git a/mobile/branding/official/configure.sh b/mobile/branding/official/configure.sh
index a30e11d91b97..55884683d154 100644
--- a/mobile/branding/official/configure.sh
+++ b/mobile/branding/official/configure.sh
@@ -1,2 +1 @@
 MOZ_APP_DISPLAYNAME=Firefox
-MOZ_APP_UA_EXTRA=Firefox
diff --git a/mobile/confvars.sh b/mobile/confvars.sh
index b8e0d200126b..d6e344f64c32 100644
--- a/mobile/confvars.sh
+++ b/mobile/confvars.sh
@@ -36,6 +36,7 @@
 # ***** END LICENSE BLOCK *****
 
 MOZ_APP_NAME=fennec
+MOZ_APP_UA_NAME=Fennec
 MOZ_BRANDING_DIRECTORY=mobile/branding/nightly
 MOZ_OFFICIAL_BRANDING_DIRECTORY=mobile/branding/official