diff --git a/browser/app/Makefile.in b/browser/app/Makefile.in
index 54e2a5dbe4a1..a705fdbd4aa0 100644
--- a/browser/app/Makefile.in
+++ b/browser/app/Makefile.in
@@ -133,7 +133,7 @@ GARBAGE += $(addprefix $(FINAL_TARGET)/defaults/pref/, firefox.js)
 
 endif
 
-ifeq ($(MOZ_WIDGET_TOOLKIT),gtk2)
+ifdef MOZ_WIDGET_GTK
 libs::
 	$(INSTALL) $(IFLAGS1) $(DIST)/branding/mozicon128.png $(FINAL_TARGET)/icons
 	$(INSTALL) $(IFLAGS1) $(DIST)/branding/default16.png  $(FINAL_TARGET)/chrome/icons/default
diff --git a/browser/base/Makefile.in b/browser/base/Makefile.in
index 71d9254c1b97..285ef15f0f1e 100644
--- a/browser/base/Makefile.in
+++ b/browser/base/Makefile.in
@@ -26,11 +26,11 @@ DEFINES += \
 	-DPRE_RELEASE_SUFFIX="$(PRE_RELEASE_SUFFIX)" \
 	$(NULL)
 
-ifneq (,$(filter windows gtk2 cocoa, $(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter windows gtk2 gtk3 cocoa, $(MOZ_WIDGET_TOOLKIT)))
 DEFINES += -DHAVE_SHELL_SERVICE=1
 endif
 
-ifneq (,$(filter windows cocoa gtk2, $(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter windows cocoa gtk2 gtk3, $(MOZ_WIDGET_TOOLKIT)))
 DEFINES += -DCONTEXT_COPY_IMAGE_CONTENTS=1
 endif
 
@@ -38,6 +38,6 @@ ifneq (,$(filter windows cocoa, $(MOZ_WIDGET_TOOLKIT)))
 DEFINES += -DCAN_DRAW_IN_TITLEBAR=1
 endif
 
-ifneq (,$(filter windows gtk2, $(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter windows gtk2 gtk3, $(MOZ_WIDGET_TOOLKIT)))
 DEFINES += -DMENUBAR_CAN_AUTOHIDE=1
 endif
diff --git a/browser/base/content/browser-sets.inc b/browser/base/content/browser-sets.inc
index 66191182e5df..f2d213b95e69 100644
--- a/browser/base/content/browser-sets.inc
+++ b/browser/base/content/browser-sets.inc
@@ -337,8 +337,8 @@
     <key keycode="&findAgainCmd.commandkey2;"  command="cmd_findPrevious" modifiers="shift"/>
 
     <key id="addBookmarkAsKb" key="&bookmarkThisPageCmd.commandkey;" command="Browser:AddBookmarkAs" modifiers="accel"/>
-# Accel+Shift+A-F are reserved on GTK2
-#ifndef MOZ_WIDGET_GTK2
+# Accel+Shift+A-F are reserved on GTK
+#ifndef MOZ_WIDGET_GTK
     <key id="bookmarkAllTabsKb" key="&bookmarkThisPageCmd.commandkey;" oncommand="PlacesCommandHook.bookmarkCurrentPages();" modifiers="accel,shift"/>
     <key id="manBookmarkKb" key="&bookmarksCmd.commandkey;" command="Browser:ShowAllBookmarks" modifiers="accel,shift"/>
 #else
diff --git a/browser/base/content/test/Makefile.in b/browser/base/content/test/Makefile.in
index 6125ccc4154b..d5713a9c6a3e 100644
--- a/browser/base/content/test/Makefile.in
+++ b/browser/base/content/test/Makefile.in
@@ -39,7 +39,7 @@ MOCHITEST_FILES = \
 		$(NULL)
 
 # test_contextmenu.html is disabled on Linux due to bug 513558
-ifneq (gtk2,$(MOZ_WIDGET_TOOLKIT))
+ifdef MOZ_WIDGET_GTK
 MOCHITEST_FILES += \
 		audio.ogg \
 		test_contextmenu.html \
diff --git a/browser/branding/nightly/Makefile.in b/browser/branding/nightly/Makefile.in
index a593682abba0..bf553dd76865 100644
--- a/browser/branding/nightly/Makefile.in
+++ b/browser/branding/nightly/Makefile.in
@@ -44,7 +44,7 @@ BRANDING_FILES := \
 	$(NULL)
 endif
 
-ifeq ($(MOZ_WIDGET_TOOLKIT),gtk2)
+ifdef MOZ_WIDGET_GTK
 BRANDING_FILES := \
 	default16.png \
 	default32.png \
diff --git a/browser/branding/unofficial/Makefile.in b/browser/branding/unofficial/Makefile.in
index a593682abba0..bf553dd76865 100644
--- a/browser/branding/unofficial/Makefile.in
+++ b/browser/branding/unofficial/Makefile.in
@@ -44,7 +44,7 @@ BRANDING_FILES := \
 	$(NULL)
 endif
 
-ifeq ($(MOZ_WIDGET_TOOLKIT),gtk2)
+ifdef MOZ_WIDGET_GTK
 BRANDING_FILES := \
 	default16.png \
 	default32.png \
diff --git a/browser/components/build/Makefile.in b/browser/components/build/Makefile.in
index a5b843c8b728..82808e7e76c9 100644
--- a/browser/components/build/Makefile.in
+++ b/browser/components/build/Makefile.in
@@ -38,7 +38,7 @@ SHARED_LIBRARY_LIBS = \
 	../dirprovider/$(LIB_PREFIX)browserdir_s.$(LIB_SUFFIX) \
 	$(NULL)
 
-ifneq (,$(filter windows cocoa gtk2, $(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter windows cocoa gtk2 gtk3, $(MOZ_WIDGET_TOOLKIT)))
 SHARED_LIBRARY_LIBS += ../shell/src/$(LIB_PREFIX)shellservice_s.$(LIB_SUFFIX)
 endif
 
@@ -57,7 +57,7 @@ SHARED_LIBRARY_LIBS += ../migration/src/$(LIB_PREFIX)migration_s.$(LIB_SUFFIX)
 
 # Mac: Need to link with CoreFoundation for Mac Migrators (PList reading code)
 # GTK2: Need to link with glib for GNOME shell service
-ifneq (,$(filter cocoa gtk2,$(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter cocoa gtk2 gtk3,$(MOZ_WIDGET_TOOLKIT)))
 EXTRA_DSO_LDOPTS += \
   $(TK_LIBS) \
   $(NULL)
diff --git a/browser/components/build/nsModule.cpp b/browser/components/build/nsModule.cpp
index a47bbf11477f..fc5734cd2554 100644
--- a/browser/components/build/nsModule.cpp
+++ b/browser/components/build/nsModule.cpp
@@ -12,7 +12,7 @@
 #include "nsWindowsShellService.h"
 #elif defined(XP_MACOSX)
 #include "nsMacShellService.h"
-#elif defined(MOZ_WIDGET_GTK2)
+#elif defined(MOZ_WIDGET_GTK)
 #include "nsGNOMEShellService.h"
 #endif
 
@@ -36,7 +36,7 @@ NS_GENERIC_FACTORY_CONSTRUCTOR(DirectoryProvider)
 NS_GENERIC_FACTORY_CONSTRUCTOR(nsWindowsShellService)
 #elif defined(XP_MACOSX)
 NS_GENERIC_FACTORY_CONSTRUCTOR(nsMacShellService)
-#elif defined(MOZ_WIDGET_GTK2)
+#elif defined(MOZ_WIDGET_GTK)
 NS_GENERIC_FACTORY_CONSTRUCTOR_INIT(nsGNOMEShellService, Init)
 #endif
 
@@ -49,7 +49,7 @@ NS_GENERIC_FACTORY_CONSTRUCTOR(nsFeedSniffer)
 NS_DEFINE_NAMED_CID(NS_BROWSERDIRECTORYPROVIDER_CID);
 #if defined(XP_WIN)
 NS_DEFINE_NAMED_CID(NS_SHELLSERVICE_CID);
-#elif defined(MOZ_WIDGET_GTK2)
+#elif defined(MOZ_WIDGET_GTK)
 NS_DEFINE_NAMED_CID(NS_SHELLSERVICE_CID);
 #endif
 NS_DEFINE_NAMED_CID(NS_FEEDSNIFFER_CID);
@@ -64,7 +64,7 @@ static const mozilla::Module::CIDEntry kBrowserCIDs[] = {
     { &kNS_BROWSERDIRECTORYPROVIDER_CID, false, NULL, DirectoryProviderConstructor },
 #if defined(XP_WIN)
     { &kNS_SHELLSERVICE_CID, false, NULL, nsWindowsShellServiceConstructor },
-#elif defined(MOZ_WIDGET_GTK2)
+#elif defined(MOZ_WIDGET_GTK)
     { &kNS_SHELLSERVICE_CID, false, NULL, nsGNOMEShellServiceConstructor },
 #endif
     { &kNS_FEEDSNIFFER_CID, false, NULL, nsFeedSnifferConstructor },
@@ -81,7 +81,7 @@ static const mozilla::Module::ContractIDEntry kBrowserContracts[] = {
     { NS_BROWSERDIRECTORYPROVIDER_CONTRACTID, &kNS_BROWSERDIRECTORYPROVIDER_CID },
 #if defined(XP_WIN)
     { NS_SHELLSERVICE_CONTRACTID, &kNS_SHELLSERVICE_CID },
-#elif defined(MOZ_WIDGET_GTK2)
+#elif defined(MOZ_WIDGET_GTK)
     { NS_SHELLSERVICE_CONTRACTID, &kNS_SHELLSERVICE_CID },
 #endif
     { NS_FEEDSNIFFER_CONTRACTID, &kNS_FEEDSNIFFER_CID },
@@ -129,4 +129,3 @@ static const mozilla::Module kBrowserModule = {
 };
 
 NSMODULE_DEFN(nsBrowserCompsModule) = &kBrowserModule;
-
diff --git a/browser/components/preferences/Makefile.in b/browser/components/preferences/Makefile.in
index 0d93ee82ad93..32c72ab28765 100644
--- a/browser/components/preferences/Makefile.in
+++ b/browser/components/preferences/Makefile.in
@@ -17,6 +17,6 @@ DEFINES += \
 	-DMOZ_MACBUNDLE_NAME=$(MOZ_MACBUNDLE_NAME) \
 	$(NULL)
 
-ifneq (,$(filter windows gtk2 cocoa, $(MOZ_WIDGET_TOOLKIT)))
+ifneq (,$(filter windows gtk2 gtk3 cocoa, $(MOZ_WIDGET_TOOLKIT)))
 DEFINES += -DHAVE_SHELL_SERVICE=1
 endif
diff --git a/browser/components/preferences/applications.js b/browser/components/preferences/applications.js
index ef192e6d9715..5633641a3f39 100644
--- a/browser/components/preferences/applications.js
+++ b/browser/components/preferences/applications.js
@@ -79,7 +79,7 @@ const PREF_AUDIO_FEED_SELECTED_READER = "browser.audioFeeds.handler.default";
 const kActionUsePlugin = 5;
 
 /*
-#ifdef MOZ_WIDGET_GTK2
+#ifdef MOZ_WIDGET_GTK
 */
 const ICON_URL_APP      = "moz-icon://dummy.exe?size=16";
 /*
diff --git a/browser/components/shell/src/Makefile.in b/browser/components/shell/src/Makefile.in
index 859da3b3ff22..6cf8aa1d7ee8 100644
--- a/browser/components/shell/src/Makefile.in
+++ b/browser/components/shell/src/Makefile.in
@@ -26,7 +26,7 @@ else
 ifeq (cocoa,$(MOZ_WIDGET_TOOLKIT))
 LIBRARY_NAME = shellservice_s
 else
-ifeq ($(MOZ_WIDGET_TOOLKIT), gtk2)
+ifdef MOZ_WIDGET_GTK
 LIBRARY_NAME = shellservice_s
 endif
 endif
diff --git a/browser/components/shell/src/moz.build b/browser/components/shell/src/moz.build
index e3129f93a73d..c5d30f01e50e 100644
--- a/browser/components/shell/src/moz.build
+++ b/browser/components/shell/src/moz.build
@@ -14,7 +14,7 @@ elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'cocoa':
     CPP_SOURCES += [
         'nsMacShellService.cpp',
     ]
-elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'gtk2':
+elif CONFIG['MOZ_WIDGET_GTK']:
     CPP_SOURCES += [
         'nsGNOMEShellService.cpp',
     ]
diff --git a/browser/components/shell/src/nsGNOMEShellService.cpp b/browser/components/shell/src/nsGNOMEShellService.cpp
index 6112fff500de..23e8896e20dc 100644
--- a/browser/components/shell/src/nsGNOMEShellService.cpp
+++ b/browser/components/shell/src/nsGNOMEShellService.cpp
@@ -27,7 +27,7 @@
 #include "imgIRequest.h"
 #include "imgIContainer.h"
 #include "prprf.h"
-#ifdef MOZ_WIDGET_GTK2
+#if defined(MOZ_WIDGET_GTK)
 #include "nsIImageToPixbuf.h"
 #endif
 #include "nsXULAppAPI.h"
@@ -368,7 +368,7 @@ nsGNOMEShellService::GetCanSetDesktopBackground(bool* aResult)
 static nsresult
 WriteImage(const nsCString& aPath, imgIContainer* aImage)
 {
-#ifndef MOZ_WIDGET_GTK2
+#if !defined(MOZ_WIDGET_GTK)
   return NS_ERROR_NOT_AVAILABLE;
 #else
   nsCOMPtr<nsIImageToPixbuf> imgToPixbuf =
diff --git a/browser/installer/Makefile.in b/browser/installer/Makefile.in
index 3b8d55c79091..4e3ab6fad4ba 100644
--- a/browser/installer/Makefile.in
+++ b/browser/installer/Makefile.in
@@ -42,8 +42,8 @@ ifdef MOZ_ENABLE_GNOME_COMPONENT
 DEFINES += -DMOZ_ENABLE_GNOME_COMPONENT=1
 endif
 
-ifeq (gtk2, $(MOZ_WIDGET_TOOLKIT))
-DEFINES += -DMOZ_GTK2=1
+ifdef MOZ_WIDGET_GTK
+DEFINES += -DMOZ_GTK=1
 endif
 
 ifdef MOZ_NATIVE_NSPR
diff --git a/browser/installer/package-manifest.in b/browser/installer/package-manifest.in
index 0916d5fde237..c69900bb62f4 100644
--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -226,7 +226,7 @@
 @BINPATH@/components/exthelper.xpt
 @BINPATH@/components/fastfind.xpt
 @BINPATH@/components/feeds.xpt
-#ifdef MOZ_GTK2
+#ifdef MOZ_GTK
 @BINPATH@/components/filepicker.xpt
 #endif
 @BINPATH@/components/find.xpt
@@ -370,7 +370,7 @@
 @BINPATH@/components/crypto-SDR.js
 @BINPATH@/components/jsconsole-clhandler.manifest
 @BINPATH@/components/jsconsole-clhandler.js
-#ifdef MOZ_GTK2
+#ifdef MOZ_GTK
 @BINPATH@/components/nsFilePicker.manifest
 @BINPATH@/components/nsFilePicker.js
 #endif
@@ -570,7 +570,7 @@
 @BINPATH@/chrome/toolkit.manifest
 @BINPATH@/chrome/recording.manifest
 @BINPATH@/chrome/recording/*
-#ifdef MOZ_GTK2
+#ifdef MOZ_GTK
 @BINPATH@/browser/chrome/icons/default/default16.png
 @BINPATH@/browser/chrome/icons/default/default32.png
 @BINPATH@/browser/chrome/icons/default/default48.png