diff --git a/libs/ardour/async_midi_port.cc b/libs/ardour/async_midi_port.cc
index 77ca62961e..00e9a363b0 100644
--- a/libs/ardour/async_midi_port.cc
+++ b/libs/ardour/async_midi_port.cc
@@ -20,6 +20,8 @@
 
 #include <iostream>
 
+#include <glibmm/timer.h>
+
 #include "pbd/error.h"
 #include "pbd/stacktrace.h"