diff --git a/gtk2_ardour/plugin_ui.cc b/gtk2_ardour/plugin_ui.cc
index 291800615d..b08b5a3a0f 100644
--- a/gtk2_ardour/plugin_ui.cc
+++ b/gtk2_ardour/plugin_ui.cc
@@ -38,6 +38,7 @@
 #include <gtkmm2ext/utils.h>
 #include <gtkmm2ext/doi.h>
 #include <gtkmm2ext/slider_controller.h>
+#include <gtkmm2ext/application.h>
 
 #include "midi++/manager.h"
 
@@ -291,8 +292,7 @@ PluginUIWindow::create_audiounit_editor (boost::shared_ptr<PluginInsert>)
         _pluginui->KeyboardFocused.connect (sigc::mem_fun (*this, &PluginUIWindow::keyboard_focused));
 	add (*box);
 
-	extern sigc::signal<void,bool> ApplicationActivationChanged;
-	ApplicationActivationChanged.connect (sigc::mem_fun (*this, &PluginUIWindow::app_activated));
+	Application::instance()->ActivationChanged.connect (mem_fun (*this, &PluginUIWindow::app_activated));
 
 	return true;
 #endif