diff --git a/gtk2_ardour/midi_channel_selector.h b/gtk2_ardour/midi_channel_selector.h
index f10c128b92..3ec2cfbd2c 100644
--- a/gtk2_ardour/midi_channel_selector.h
+++ b/gtk2_ardour/midi_channel_selector.h
@@ -25,6 +25,7 @@
 #include "sigc++/trackable.h"
 
 #include "gtkmm/table.h"
+#include "gtkmm/box.h"
 #include "gtkmm/button.h"
 #include "gtkmm/radiobutton.h"
 #include "gtkmm/label.h"