diff --git a/src/gui/gtk-lumiera.hpp b/src/gui/gtk-lumiera.hpp
index 180148f7f..a25927712 100644
--- a/src/gui/gtk-lumiera.hpp
+++ b/src/gui/gtk-lumiera.hpp
@@ -31,6 +31,7 @@
 #include <gtkmm.h>
 #include <nobug.h>
 #include <vector>
+#include <boost/utility.hpp>
 
 extern "C" {
 #include <gavl/gavltime.h>
@@ -91,7 +92,7 @@ static const gchar* AppAuthors[] = {
 /**
  *  The main application class.
  */
-class GtkLumiera
+class GtkLumiera : private boost::noncopyable
 {
 public:
   int main(int argc, char *argv[]);
diff --git a/src/gui/window-manager.hpp b/src/gui/window-manager.hpp
index c25a763ef..49c69ea50 100644
--- a/src/gui/window-manager.hpp
+++ b/src/gui/window-manager.hpp
@@ -35,7 +35,7 @@ namespace gui {
 /**
  * The centralised manager of all lumiera-gui's windows.
  **/
-class WindowManager
+class WindowManager : private boost::noncopyable
 {
 public:
   /**