diff --git a/libs/gtkmm2ext/gtkmm2ext/auto_spin.h b/libs/gtkmm2ext/gtkmm2ext/auto_spin.h
index b692a7ccdc..4eab2dae98 100644
--- a/libs/gtkmm2ext/gtkmm2ext/auto_spin.h
+++ b/libs/gtkmm2ext/gtkmm2ext/auto_spin.h
@@ -20,6 +20,10 @@
 #ifndef __gtkmm2ext_auto_spin_h__
 #define __gtkmm2ext_auto_spin_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <gtkmm.h>
 
 namespace Gtkmm2ext {
diff --git a/libs/gtkmm2ext/gtkmm2ext/click_box.h b/libs/gtkmm2ext/gtkmm2ext/click_box.h
index 8f9655e2bf..ea0041e540 100644
--- a/libs/gtkmm2ext/gtkmm2ext/click_box.h
+++ b/libs/gtkmm2ext/gtkmm2ext/click_box.h
@@ -20,6 +20,10 @@
 #ifndef __gtkmm2ext_click_box_h__
 #define __gtkmm2ext_click_box_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <string>
 #include <gtkmm.h>
 
diff --git a/libs/gtkmm2ext/gtkmm2ext/doi.h b/libs/gtkmm2ext/gtkmm2ext/doi.h
index 6ad1f7dd94..f61127dd74 100644
--- a/libs/gtkmm2ext/gtkmm2ext/doi.h
+++ b/libs/gtkmm2ext/gtkmm2ext/doi.h
@@ -20,6 +20,10 @@
 #ifndef __ardour_gtk_doi_h__
 #define __ardour_gtk_doi_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <gtkmm.h>
 
 /* XXX g++ 2.95 can't compile this as pair of member function templates */
diff --git a/libs/gtkmm2ext/gtkmm2ext/popup.h b/libs/gtkmm2ext/gtkmm2ext/popup.h
index 1db357341d..994932e733 100644
--- a/libs/gtkmm2ext/gtkmm2ext/popup.h
+++ b/libs/gtkmm2ext/gtkmm2ext/popup.h
@@ -20,6 +20,10 @@
 #ifndef __qui_popup_h__
 #define __qui_popup_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <string>
 #include <gtkmm.h>
 
diff --git a/libs/gtkmm2ext/gtkmm2ext/selector.h b/libs/gtkmm2ext/gtkmm2ext/selector.h
index 841742db03..56e075a242 100644
--- a/libs/gtkmm2ext/gtkmm2ext/selector.h
+++ b/libs/gtkmm2ext/gtkmm2ext/selector.h
@@ -19,6 +19,10 @@
 #ifndef __gtkselector_h__
 #define __gtkselector_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <string>
 #include <vector>
 
diff --git a/libs/gtkmm2ext/gtkmm2ext/slider_controller.h b/libs/gtkmm2ext/gtkmm2ext/slider_controller.h
index 4c6a5cb41d..42ed05a761 100644
--- a/libs/gtkmm2ext/gtkmm2ext/slider_controller.h
+++ b/libs/gtkmm2ext/gtkmm2ext/slider_controller.h
@@ -19,6 +19,10 @@
 #ifndef __gtkmm2ext_slider_controller_h__
 #define __gtkmm2ext_slider_controller_h__
 
+#ifdef interface
+#undef interface
+#endif
+
 #include <gtkmm.h>
 #include <gtkmm2ext/popup.h>
 #include <gtkmm2ext/pixfader.h>