diff --git a/gtk2_ardour/audio_clock.cc b/gtk2_ardour/audio_clock.cc
index 4c4361185e..130729a7af 100644
--- a/gtk2_ardour/audio_clock.cc
+++ b/gtk2_ardour/audio_clock.cc
@@ -63,6 +63,7 @@ using namespace ARDOUR_UI_UTILS;
 using namespace ArdourWidgets;
 using namespace PBD;
 using namespace Gtk;
+using namespace Gtkmm2ext;
 using namespace std;
 using namespace Temporal;
 
diff --git a/gtk2_ardour/loudness_dialog.cc b/gtk2_ardour/loudness_dialog.cc
index e10a80c0d2..aedcfea234 100644
--- a/gtk2_ardour/loudness_dialog.cc
+++ b/gtk2_ardour/loudness_dialog.cc
@@ -53,6 +53,7 @@
 
 using namespace Gtk;
 using namespace ARDOUR;
+using namespace Gtkmm2ext;
 using namespace ArdourWidgets;
 
 bool LoudnessDialog::_first_time = true;
diff --git a/gtk2_ardour/ui_config.h b/gtk2_ardour/ui_config.h
index c691ae84eb..fed88ad5e3 100644
--- a/gtk2_ardour/ui_config.h
+++ b/gtk2_ardour/ui_config.h
@@ -39,12 +39,12 @@
 #include "pbd/xml++.h"
 
 #include "gtkmm2ext/colors.h"
-#include "widgets/ui_config.h"
+#include "gtkmm2ext/ui_config.h"
 
 #include "editing.h"
 #include "utils.h"
 
-class UIConfiguration : public ArdourWidgets::UIConfigurationBase
+class UIConfiguration : public Gtkmm2ext::UIConfigurationBase
 {
 private:
 	UIConfiguration ();