diff --git a/build/moz.configure/old.configure b/build/moz.configure/old.configure
index 18850d2e37..bfa098fbbc 100644
--- a/build/moz.configure/old.configure
+++ b/build/moz.configure/old.configure
@@ -164,6 +164,7 @@ def old_configure_options(*options):
     '--enable-negotiateauth',
     '--enable-nfc',
     '--enable-npapi',
+    '--enable-npapi-gtk2',
     '--enable-nspr-build',
     '--enable-official-branding',
     '--enable-official-vendor',
diff --git a/dom/plugins/ipc/PluginInstanceChild.cpp b/dom/plugins/ipc/PluginInstanceChild.cpp
index 599466c6b3..61e56a9438 100644
--- a/dom/plugins/ipc/PluginInstanceChild.cpp
+++ b/dom/plugins/ipc/PluginInstanceChild.cpp
@@ -55,7 +55,12 @@ using namespace std;
 #include <gtk/gtk.h>
 #include <gdk/gdkx.h>
 #include <gdk/gdk.h>
+#if (GTK_MAJOR_VERSION == 3)
+#include <gtk/gtkx.h>
+#endif
+#ifdef MOZ_ENABLE_NPAPI_GTK2
 #include "gtk2xtbin.h"
+#endif
 
 #elif defined(OS_WIN)
 
@@ -208,7 +213,9 @@ PluginInstanceChild::PluginInstanceChild(const NPPluginFuncs* aPluginIface,
     memset(&mWsInfo, 0, sizeof(mWsInfo));
 #ifdef MOZ_WIDGET_GTK
     mWsInfo.display = nullptr;
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     mXtClient.top_widget = nullptr;
+#endif
 #else
     mWsInfo.display = DefaultXDisplay();
 #endif
@@ -620,15 +627,17 @@ PluginInstanceChild::NPN_SetValue(NPPVariable aVar, void* aValue)
         NPWindowType newWindowType = windowed ? NPWindowTypeWindow : NPWindowTypeDrawable;
 #ifdef MOZ_WIDGET_GTK
         if (mWindow.type != newWindowType && mWsInfo.display) {
-           // plugin type has been changed but we already have a valid display
-           // so update it for the recent plugin mode
-           if (mXEmbed || !windowed) {
-               // Use default GTK display for XEmbed and windowless plugins
-               mWsInfo.display = DefaultXDisplay();
-           }
-           else {
-               mWsInfo.display = xt_client_get_display();
-           }
+            // plugin type has been changed but we already have a valid display
+            // so update it for the recent plugin mode
+#ifdef MOZ_ENABLE_NPAPI_GTK2
+            if (!mXEmbed && windowed) {
+                mWsInfo.display = xt_client_get_display();
+            } else
+#endif
+            {
+                // Use default GTK display for XEmbed and windowless plugins.
+                mWsInfo.display = DefaultXDisplay();
+            }
         }
 #endif
         mWindow.type = newWindowType;
@@ -1214,12 +1223,18 @@ bool PluginInstanceChild::CreateWindow(const NPRemoteWindow& aWindow)
     if (mXEmbed) {
         mWindow.window = reinterpret_cast<void*>(aWindow.window);
     }
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     else {
         Window browserSocket = (Window)(aWindow.window);
         xt_client_init(&mXtClient, mWsInfo.visual, mWsInfo.colormap, mWsInfo.depth);
         xt_client_create(&mXtClient, browserSocket, mWindow.width, mWindow.height); 
         mWindow.window = (void *)XtWindow(mXtClient.child_widget);
-    }  
+    }
+#else
+    else {
+        mWindow.window = reinterpret_cast<void*>(aWindow.window);
+    }
+#endif
 #else
     mWindow.window = reinterpret_cast<void*>(aWindow.window);
 #endif
@@ -1239,7 +1254,7 @@ void PluginInstanceChild::DeleteWindow()
   if (!mWindow.window)
       return;
 
-#ifdef MOZ_WIDGET_GTK
+#ifdef MOZ_ENABLE_NPAPI_GTK2
   if (mXtClient.top_widget) {     
       xt_client_unrealize(&mXtClient);
       xt_client_destroy(&mXtClient); 
@@ -1321,7 +1336,7 @@ PluginInstanceChild::AnswerNPP_SetWindow(const NPRemoteWindow& aWindow)
         CreateWindow(aWindow);
     }
 
-#ifdef MOZ_WIDGET_GTK
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     if (mXEmbed && gtk_check_version(2,18,7) != nullptr) { // older
         if (aWindow.type == NPWindowTypeWindow) {
             GdkWindow* socket_window = gdk_window_lookup(static_cast<GdkNativeWindow>(aWindow.window));
@@ -1456,19 +1471,27 @@ PluginInstanceChild::Initialize()
     if (mWindow.type == NPWindowTypeWindow) {
         AnswerNPP_GetValue_NPPVpluginNeedsXEmbed(&mXEmbed, &rv);
 
+#ifdef MOZ_ENABLE_NPAPI_GTK2
         // Set up Xt loop for windowed plugins without XEmbed support
         if (!mXEmbed) {
            xt_client_xloop_create();
         }
+#endif
     }
 
-    // Use default GTK display for XEmbed and windowless plugins
+    // Use default GTK display for XEmbed and windowless plugins.
     if (mXEmbed || mWindow.type != NPWindowTypeWindow) {
         mWsInfo.display = DefaultXDisplay();
     }
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     else {
         mWsInfo.display = xt_client_get_display();
     }
+#else
+    else {
+        mWsInfo.display = DefaultXDisplay();
+    }
+#endif
 #endif 
 
     return true;
@@ -4656,7 +4679,7 @@ PluginInstanceChild::Destroy()
 
     mPendingAsyncCalls.Clear();
     
-#ifdef MOZ_WIDGET_GTK
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     if (mWindow.type == NPWindowTypeWindow && !mXEmbed) {
       xt_client_xloop_destroy();
     }
diff --git a/dom/plugins/ipc/PluginInstanceChild.h b/dom/plugins/ipc/PluginInstanceChild.h
index ec8a7675ef..57b88a30fb 100644
--- a/dom/plugins/ipc/PluginInstanceChild.h
+++ b/dom/plugins/ipc/PluginInstanceChild.h
@@ -36,7 +36,7 @@
 
 #include <map>
 
-#ifdef MOZ_WIDGET_GTK
+#ifdef MOZ_ENABLE_NPAPI_GTK2
 #include "gtk2xtbin.h"
 #endif
 
@@ -462,6 +462,8 @@ private:
     NPSetWindowCallbackStruct mWsInfo;
 #ifdef MOZ_WIDGET_GTK
     bool mXEmbed;
+#endif
+#ifdef MOZ_ENABLE_NPAPI_GTK2
     XtClient mXtClient;
 #endif
 #elif defined(OS_WIN)
diff --git a/dom/plugins/ipc/PluginModuleChild.cpp b/dom/plugins/ipc/PluginModuleChild.cpp
index 035a54c9a4..4bdaa613c5 100644
--- a/dom/plugins/ipc/PluginModuleChild.cpp
+++ b/dom/plugins/ipc/PluginModuleChild.cpp
@@ -12,6 +12,9 @@
 
 #ifdef MOZ_WIDGET_GTK
 #include <gtk/gtk.h>
+#if (GTK_MAJOR_VERSION == 3)
+#include <gtk/gtkx.h>
+#endif
 #endif
 
 #include "nsIFile.h"
@@ -1101,7 +1104,11 @@ _getvalue(NPP aNPP,
                 return InstCast(aNPP)->NPN_GetValue(aVariable, aValue);
             } 
             else {
+#ifdef MOZ_ENABLE_NPAPI_GTK2
                 *(void **)aValue = xt_client_get_display();
+#else
+                *(void **)aValue = DefaultXDisplay();
+#endif
             }          
             return NPERR_NO_ERROR;
         }
diff --git a/dom/plugins/ipc/moz.build b/dom/plugins/ipc/moz.build
index 9afa6f298e..5bc3474413 100644
--- a/dom/plugins/ipc/moz.build
+++ b/dom/plugins/ipc/moz.build
@@ -143,11 +143,13 @@ LOCAL_INCLUDES += [
 
 DEFINES['FORCE_PR_LOG'] = True
 
-if CONFIG['MOZ_WIDGET_TOOLKIT'] != 'gtk3':
-    CXXFLAGS += CONFIG['TK_CFLAGS']
-else:
+if (CONFIG['MOZ_WIDGET_TOOLKIT'] == 'gtk3' and
+        CONFIG['MOZ_ENABLE_NPAPI'] and
+        CONFIG['MOZ_ENABLE_NPAPI_GTK2']):
     # Force build against gtk+2 for struct offsets and such.
     CXXFLAGS += CONFIG['MOZ_GTK2_CFLAGS']
+else:
+    CXXFLAGS += CONFIG['TK_CFLAGS']
 
 CXXFLAGS += CONFIG['MOZ_CAIRO_CFLAGS']
 
diff --git a/old-configure.in b/old-configure.in
index 2eccf92eaf..3832889919 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -2146,12 +2146,26 @@ MOZ_ARG_DISABLE_BOOL(npapi,
     MOZ_ENABLE_NPAPI=,
     MOZ_ENABLE_NPAPI=1)
 
+MOZ_ENABLE_NPAPI_GTK2=1
+
+MOZ_ARG_DISABLE_BOOL(npapi-gtk2,
+[  --disable-npapi-gtk2     Disable GTK2 support for NPAPI plugins ],
+    MOZ_ENABLE_NPAPI_GTK2=
+    MOZ_DISABLE_NPAPI_GTK2=1,
+    MOZ_ENABLE_NPAPI_GTK2=1)
+
 if test "$MOZ_ENABLE_NPAPI"
 then
     AC_DEFINE(MOZ_ENABLE_NPAPI)
 fi
 
+if test "$MOZ_ENABLE_NPAPI" -a "$MOZ_ENABLE_NPAPI_GTK2"
+then
+    AC_DEFINE(MOZ_ENABLE_NPAPI_GTK2)
+fi
+
 AC_SUBST(MOZ_ENABLE_NPAPI)
+AC_SUBST(MOZ_ENABLE_NPAPI_GTK2)
 
 dnl ========================================================
 dnl =
@@ -2200,6 +2214,10 @@ gtk*)
     ;;
 esac
 
+if test "$MOZ_WIDGET_TOOLKIT" = gtk2 -a "$MOZ_DISABLE_NPAPI_GTK2"; then
+  AC_MSG_ERROR([--disable-npapi-gtk2 cannot be used with GTK2 browser builds.])
+fi
+
 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 $GDK_PACKAGES)
@@ -2210,8 +2228,9 @@ if test "$COMPILE_ENVIRONMENT"; then
     dnl are suppressed by widget/gtk/compat-gtk3/gdk/gdkversionmacros.h.
     AC_DEFINE_UNQUOTED(GDK_VERSION_MAX_ALLOWED,$GDK_VERSION_MAX_ALLOWED)
     GLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_32
-    dnl We want to check GTK2 packages if NPAPI is enabled, even if building with GTK3.
-    if test "$MOZ_ENABLE_NPAPI"; then
+    dnl GTK2 NPAPI plugin support needs GTK2 packages, even when the browser
+    dnl itself is built against GTK3.
+    if test "$MOZ_ENABLE_NPAPI" -a "$MOZ_ENABLE_NPAPI_GTK2"; then
       MOZ_CHECK_GTK2=1
     fi
   fi
@@ -2229,7 +2248,7 @@ if test "$COMPILE_ENVIRONMENT"; then
 
     if test "$MOZ_CHECK_GTK2"; then
       PKG_CHECK_MODULES(MOZ_GTK2, gtk+-2.0 >= $GTK2_VERSION gtk+-unix-print-2.0 glib-2.0 >= $GLIB_VERSION gobject-2.0 $GDK_PACKAGES, ,
-                               [AC_MSG_ERROR([ * * * Could not find gtk+-2.0. Required for NPAPI plugins. To build without NPAPI, add --disable-npapi to your .mozconfig and clobber.])])
+                               [AC_MSG_ERROR([ * * * Could not find gtk+-2.0. Required for GTK2 browser builds and GTK2 NPAPI plugin support. To build a GTK3 browser with NPAPI but without GTK2 NPAPI plugin support, add --disable-npapi-gtk2 to your .mozconfig and clobber.])])
     MOZ_GTK2_CFLAGS="-I${_topsrcdir}/widget/gtk/compat $MOZ_GTK2_CFLAGS"
     fi
   fi
diff --git a/widget/gtk/mozgtk/moz.build b/widget/gtk/mozgtk/moz.build
index 43f94aabfe..99d10056d8 100644
--- a/widget/gtk/mozgtk/moz.build
+++ b/widget/gtk/mozgtk/moz.build
@@ -3,4 +3,7 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-DIRS += ['stub', 'gtk2', 'gtk3']
+DIRS += ['stub', 'gtk3']
+
+if CONFIG['MOZ_ENABLE_NPAPI_GTK2']:
+    DIRS += ['gtk2']
diff --git a/widget/gtk/mozgtk/stub/moz.build b/widget/gtk/mozgtk/stub/moz.build
index 7713bfaafd..c8e35b37ca 100644
--- a/widget/gtk/mozgtk/stub/moz.build
+++ b/widget/gtk/mozgtk/stub/moz.build
@@ -7,9 +7,12 @@ SOURCES += [
     '../mozgtk.c',
 ]
 
-for var in ('COMMON_SYMBOLS', 'GTK2_SYMBOLS', 'GTK3_SYMBOLS'):
+for var in ('COMMON_SYMBOLS', 'GTK3_SYMBOLS'):
     DEFINES[var] = True
 
+if CONFIG['MOZ_ENABLE_NPAPI_GTK2']:
+    DEFINES['GTK2_SYMBOLS'] = True
+
 SharedLibrary('mozgtk_stub')
 
 SONAME = 'mozgtk'
diff --git a/widget/moz.build b/widget/moz.build
index 2d40447821..6b49e35270 100644
--- a/widget/moz.build
+++ b/widget/moz.build
@@ -52,7 +52,8 @@ if toolkit in ('cocoa', 'gtk2', 'gtk3'):
 if 'gtk' in CONFIG['MOZ_WIDGET_TOOLKIT']:
     DIRS += ['gtk']
 
-    if CONFIG['MOZ_X11'] and CONFIG['MOZ_ENABLE_NPAPI']:
+    if (CONFIG['MOZ_X11'] and CONFIG['MOZ_ENABLE_NPAPI'] and
+            CONFIG['MOZ_ENABLE_NPAPI_GTK2']):
         DIRS += ['gtkxtbin']
 
 XPIDL_SOURCES += [