diff --git a/libs/ardour/test/midi_clock_slave_test.h b/libs/ardour/test/midi_clock_slave_test.h
index 5cb40db169..74da5ed620 100644
--- a/libs/ardour/test/midi_clock_slave_test.h
+++ b/libs/ardour/test/midi_clock_slave_test.h
@@ -22,7 +22,7 @@
 #include <cppunit/extensions/HelperMacros.h>
 
 #include "ardour/tempo.h"
-#include "ardour/slave.h"
+#include "ardour/transport_master.h"
 
 namespace ARDOUR {