diff --git a/libs/ardour/ardour/step_sequencer.h b/libs/ardour/ardour/step_sequencer.h
index 37e9dba275..33d34885b3 100644
--- a/libs/ardour/ardour/step_sequencer.h
+++ b/libs/ardour/ardour/step_sequencer.h
@@ -23,7 +23,6 @@
 #include <unistd.h>
 
 #include <boost/atomic.hpp>
-#include <boost/rational.hpp>
 #include <boost/intrusive/list.hpp>
 
 #include <glibmm/threads.h>