diff --git a/accessible/atk/moz.build b/accessible/atk/moz.build
index dae3f86a6049..e177383eec04 100644
--- a/accessible/atk/moz.build
+++ b/accessible/atk/moz.build
@@ -43,7 +43,7 @@ LOCAL_INCLUDES += [
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     CFLAGS += CONFIG['TK_CFLAGS']
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
diff --git a/accessible/base/moz.build b/accessible/base/moz.build
index 4e5f6a904c82..c8c6c2f22098 100644
--- a/accessible/base/moz.build
+++ b/accessible/base/moz.build
@@ -73,10 +73,11 @@ LOCAL_INCLUDES += [
     '/layout/xul/tree/',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     LOCAL_INCLUDES += [
         '/accessible/atk',
     ]
+    CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'windows':
     LOCAL_INCLUDES += [
         '/accessible/windows/ia2',
@@ -93,7 +94,4 @@ else:
 
 FINAL_LIBRARY = 'xul'
 
-if CONFIG['MOZ_ENABLE_GTK']:
-    CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
-
 include('/ipc/chromium/chromium-config.mozbuild')
diff --git a/accessible/generic/moz.build b/accessible/generic/moz.build
index f1a260388829..28b65335aada 100644
--- a/accessible/generic/moz.build
+++ b/accessible/generic/moz.build
@@ -36,7 +36,7 @@ LOCAL_INCLUDES += [
     '/layout/xul',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     LOCAL_INCLUDES += [
         '/accessible/atk',
     ]
diff --git a/accessible/html/moz.build b/accessible/html/moz.build
index 0575247f5f17..057b9e168d14 100644
--- a/accessible/html/moz.build
+++ b/accessible/html/moz.build
@@ -24,7 +24,7 @@ LOCAL_INCLUDES += [
     '/layout/xul',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     LOCAL_INCLUDES += [
         '/accessible/atk',
     ]
diff --git a/accessible/ipc/moz.build b/accessible/ipc/moz.build
index 822340225346..f7c3a7a859b4 100644
--- a/accessible/ipc/moz.build
+++ b/accessible/ipc/moz.build
@@ -27,7 +27,7 @@ if CONFIG['ACCESSIBILITY']:
         '../xpcom',
     ]
 
-    if CONFIG['MOZ_ENABLE_GTK']:
+    if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
         LOCAL_INCLUDES += [
             '/accessible/atk',
         ]
diff --git a/accessible/moz.build b/accessible/moz.build
index 993d2202937f..3e8485aff6c5 100644
--- a/accessible/moz.build
+++ b/accessible/moz.build
@@ -6,7 +6,7 @@
 
 toolkit = CONFIG['MOZ_WIDGET_TOOLKIT']
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in toolkit:
     DIRS += ['atk']
 elif toolkit == 'windows':
     DIRS += ['windows']
diff --git a/accessible/xpcom/moz.build b/accessible/xpcom/moz.build
index 42d940316d89..38c96e81116c 100644
--- a/accessible/xpcom/moz.build
+++ b/accessible/xpcom/moz.build
@@ -33,7 +33,7 @@ LOCAL_INCLUDES += [
     '/accessible/generic',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     LOCAL_INCLUDES += [
         '/accessible/atk',
     ]
diff --git a/accessible/xul/moz.build b/accessible/xul/moz.build
index 37ba0059ca6b..a1dafd9b1953 100644
--- a/accessible/xul/moz.build
+++ b/accessible/xul/moz.build
@@ -29,7 +29,7 @@ LOCAL_INCLUDES += [
     '/layout/xul/tree',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     LOCAL_INCLUDES += [
         '/accessible/atk',
     ]
diff --git a/chrome/moz.build b/chrome/moz.build
index 724f39cb32e1..18a060211743 100644
--- a/chrome/moz.build
+++ b/chrome/moz.build
@@ -36,5 +36,5 @@ LOCAL_INCLUDES += [
     '/xpcom/components'
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     CXXFLAGS += CONFIG['TK_CFLAGS']
diff --git a/dom/plugins/base/moz.build b/dom/plugins/base/moz.build
index 1706160ebfea..4bdda2ca94d2 100644
--- a/dom/plugins/base/moz.build
+++ b/dom/plugins/base/moz.build
@@ -72,7 +72,7 @@ else:
     UNIFIED_SOURCES += [
         'nsPluginsDirUnix.cpp',
     ]
-    if CONFIG['MOZ_ENABLE_GTK']:
+    if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
         # This file cannot be built in unified mode because of name clashes in X11 headers.
         SOURCES += [
             'nsPluginNativeWindowGtk.cpp',
diff --git a/old-configure.in b/old-configure.in
index 4c6862913156..85b8a842b94b 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -3431,7 +3431,6 @@ windows)
     ;;
 
 gtk3)
-    MOZ_ENABLE_GTK=1
     MOZ_ENABLE_XREMOTE=1
     MOZ_GL_DEFAULT_PROVIDER=GLX
 
@@ -3446,7 +3445,6 @@ gtk3)
     ;;
 
 gtk2)
-    MOZ_ENABLE_GTK=1
     MOZ_ENABLE_XREMOTE=1
     MOZ_GL_DEFAULT_PROVIDER=GLX
 
@@ -3532,6 +3530,14 @@ if test "$MOZ_INSTRUMENT_EVENT_LOOP"; then
    AC_DEFINE(MOZ_INSTRUMENT_EVENT_LOOP)
 fi
 
+dnl there are a lot of tests on MOZ_ENABLE_GTK below, that are more convenient
+dnl to keep that way than testing against MOZ_WIDGET_TOOLKIT
+case "$MOZ_WIDGET_TOOLKIT" in
+gtk*)
+    MOZ_ENABLE_GTK=1
+    ;;
+esac
+
 if test "$COMPILE_ENVIRONMENT"; then
   if test "$MOZ_WIDGET_TOOLKIT" = gtk3; then
     PKG_CHECK_MODULES(MOZ_GTK3, gtk+-3.0 >= $GTK3_VERSION gtk+-unix-print-3.0 glib-2.0 gobject-2.0 $GDK_PACKAGES)
@@ -3792,7 +3798,6 @@ AC_SUBST(GTK_CONFIG)
 AC_SUBST_LIST(TK_CFLAGS)
 AC_SUBST_LIST(TK_LIBS)
 
-AC_SUBST(MOZ_ENABLE_GTK)
 AC_SUBST(MOZ_ENABLE_QT)
 AC_SUBST(MOZ_ENABLE_QTNETWORK)
 AC_SUBST(MOZ_ENABLE_QMSYSTEM2)
diff --git a/toolkit/components/remote/moz.build b/toolkit/components/remote/moz.build
index e1ba3cecc078..5b81eab78180 100644
--- a/toolkit/components/remote/moz.build
+++ b/toolkit/components/remote/moz.build
@@ -14,7 +14,7 @@ SOURCES += [
     'nsXRemoteService.cpp',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     SOURCES += [
         'nsGTKRemoteService.cpp',
     ]
diff --git a/toolkit/crashreporter/client/moz.build b/toolkit/crashreporter/client/moz.build
index 8d8e96e4399d..1df3f186666b 100644
--- a/toolkit/crashreporter/client/moz.build
+++ b/toolkit/crashreporter/client/moz.build
@@ -49,7 +49,7 @@ elif CONFIG['OS_ARCH'] == 'SunOS':
         'breakpad_solaris_common_s',
     ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     UNIFIED_SOURCES += [
         'crashreporter_gtk_common.cpp',
         'crashreporter_linux.cpp',
diff --git a/toolkit/mozapps/update/updater/updater-common.build b/toolkit/mozapps/update/updater/updater-common.build
index f4b40ccae9c1..1f238a4952f6 100644
--- a/toolkit/mozapps/update/updater/updater-common.build
+++ b/toolkit/mozapps/update/updater/updater-common.build
@@ -67,7 +67,7 @@ else:
         'bz2',
     ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     have_progressui = 1
     srcs += [
         'progressui_gtk.cpp',
diff --git a/toolkit/system/gnome/moz.build b/toolkit/system/gnome/moz.build
index 0ecde073653e..e8ca72d3a89f 100644
--- a/toolkit/system/gnome/moz.build
+++ b/toolkit/system/gnome/moz.build
@@ -33,7 +33,7 @@ CXXFLAGS += CONFIG['MOZ_GIO_CFLAGS']
 CXXFLAGS += CONFIG['GLIB_CFLAGS']
 CXXFLAGS += CONFIG['MOZ_DBUS_GLIB_CFLAGS']
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     CXXFLAGS += CONFIG['TK_CFLAGS']
 
 if CONFIG['GNU_CXX']:
diff --git a/toolkit/toolkit.mozbuild b/toolkit/toolkit.mozbuild
index a4194d66c996..5cad0f681380 100644
--- a/toolkit/toolkit.mozbuild
+++ b/toolkit/toolkit.mozbuild
@@ -155,7 +155,7 @@ DIRS += [
     '/toolkit/library',
 ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     DIRS += ['/toolkit/system/gnome']
 
 DIRS += ['/addon-sdk']
diff --git a/toolkit/xre/moz.build b/toolkit/xre/moz.build
index 002987c5fdf2..098e160bf8f1 100644
--- a/toolkit/xre/moz.build
+++ b/toolkit/xre/moz.build
@@ -52,7 +52,7 @@ elif CONFIG['MOZ_WIDGET_TOOLKIT'] == 'qt':
         'nsNativeAppSupportQt.cpp',
         'nsQAppInstance.cpp',
     ]
-elif CONFIG['MOZ_ENABLE_GTK']:
+elif 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     UNIFIED_SOURCES += [
         'nsNativeAppSupportUnix.cpp',
     ]
diff --git a/uriloader/exthandler/moz.build b/uriloader/exthandler/moz.build
index b2aaa70660f6..13e1a999f86e 100644
--- a/uriloader/exthandler/moz.build
+++ b/uriloader/exthandler/moz.build
@@ -78,7 +78,7 @@ else:
         osdir + '/nsOSHelperAppService.cpp',
     ]
 
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     UNIFIED_SOURCES += [
         'unix/nsGNOMERegistry.cpp',
         'unix/nsMIMEInfoUnix.cpp',
diff --git a/widget/moz.build b/widget/moz.build
index 953afe9de6fe..f7ef2b3b270f 100644
--- a/widget/moz.build
+++ b/widget/moz.build
@@ -49,7 +49,7 @@ TEST_DIRS += ['tests']
 # multiple implementations of widget can be built on the same
 # source tree.
 #
-if CONFIG['MOZ_ENABLE_GTK']:
+if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     DIRS += ['gtk']
 
     if CONFIG['MOZ_X11']: