diff --git a/libs/ardour/ardour/step_sequencer.h b/libs/ardour/ardour/step_sequencer.h
index 8396002438..e457f8b498 100644
--- a/libs/ardour/ardour/step_sequencer.h
+++ b/libs/ardour/ardour/step_sequencer.h
@@ -22,6 +22,8 @@
 #include <vector>
 #include <unistd.h>
 
+#include <boost/rational.hpp>
+
 #include <glibmm/threads.h>
 
 #include "pbd/stateful.h"
@@ -50,6 +52,8 @@ class Step : public PBD::Stateful {
 		RelativePitch
 	};
 
+	typedef boost::rational<int> DurationRatio;
+
 	Step (StepSequence&, Temporal::Beats const & beat);
 	~Step ();
 
@@ -59,7 +63,7 @@ class Step : public PBD::Stateful {
 
 	void adjust_velocity (int amt);
 	void adjust_pitch (int amt);
-	void adjust_duration (double amt);
+	void adjust_duration (DurationRatio const & amt);
 	void adjust_octave (int amt);
 
 	Mode mode() const { return _mode; }
@@ -68,8 +72,8 @@ class Step : public PBD::Stateful {
 	double note (size_t n = 0) const { return _notes[n].number; }
 	double velocity (size_t n = 0) const { return _notes[n].velocity; }
 
-	double duration () const { return _duration; }
-	void set_duration (double duration);
+	DurationRatio duration () const { return _duration; }
+	void set_duration (DurationRatio const &);
 
 	void set_offset (Temporal::Beats const &, size_t n = 0);
 	Temporal::Beats offset (size_t n = 0) const { return _notes[n].offset; }
@@ -109,8 +113,8 @@ class Step : public PBD::Stateful {
 	bool               _skipped;
 	Mode               _mode;
 	int                _octave_shift;
-	double             _duration;
-	
+	DurationRatio      _duration;
+
 	struct ParameterValue {
 		int parameter;
 		double value;
diff --git a/libs/ardour/step_sequencer.cc b/libs/ardour/step_sequencer.cc
index 43c180cccb..8134ab351e 100644
--- a/libs/ardour/step_sequencer.cc
+++ b/libs/ardour/step_sequencer.cc
@@ -39,7 +39,7 @@ Step::Step (StepSequence &s, Temporal::Beats const & b)
 	, _skipped (false)
 	, _mode (AbsolutePitch)
 	, _octave_shift (0)
-	, _duration (1.0)
+	, _duration (1)
 {
 	std::cerr << "step @ " << b << std::endl;
 
@@ -105,16 +105,20 @@ Step::set_enabled (bool yn)
 }
 
 void
-Step::adjust_duration (double amt)
+Step::adjust_duration (DurationRatio const & amt)
 {
-	const double new_dur = _duration + amt;
+	set_duration (_duration + amt);
+}
 
-	if (new_dur > 1.0) {
-		_duration = 1.0;
-	} else if (new_dur < 1.0/64.0) {
-		_duration = 0.0;
+void
+Step::set_duration (DurationRatio const & dur)
+{
+	if (dur > 1.0) {
+		_duration = DurationRatio (1);
+	} else if (dur < DurationRatio()) {
+		_duration = DurationRatio ();
 	} else {
-		_duration = new_dur;
+		_duration = dur;
 	}
 
 	PropertyChange pc;
@@ -236,6 +240,11 @@ Step::check_note (size_t n, MidiBuffer& buf, bool running, samplepos_t start_sam
 
 	}
 
+	if (_duration == DurationRatio ()) {
+		/* no duration, so no new notes on */
+		return;
+	}
+
 	if (note.number < 0) {
 		/* note not set .. ignore */
 		return;
@@ -304,10 +313,10 @@ Step::check_note (size_t n, MidiBuffer& buf, bool running, samplepos_t start_sam
 
 			note.off_at = note_on_time;
 
-			if (_duration == 1.0) {
+			if (_duration == DurationRatio (1)) {
 				note.off_at += Temporal::Beats (0, _sequence.step_size().to_ticks() - 1);
 			} else {
-				note.off_at += Temporal::Beats (0, _sequence.step_size().to_ticks() * _duration);
+				note.off_at += Temporal::Beats (0, (_sequence.step_size().to_ticks() * _duration.numerator()) / _duration.denominator());
 			}
 		}
 	}