diff --git a/libgambatte/src/sound/duty_unit.cpp b/libgambatte/src/sound/duty_unit.cpp
index 0c9480c7..9401dfe8 100644
--- a/libgambatte/src/sound/duty_unit.cpp
+++ b/libgambatte/src/sound/duty_unit.cpp
@@ -21,7 +21,6 @@
 
 static inline bool toOutState(const unsigned duty, const unsigned pos) {
 	static const unsigned char duties[4] = { 0x80, 0x81, 0xE1, 0x7E };
-
 	return duties[duty] >> pos & 1;
 }
 
@@ -31,6 +30,16 @@ static inline unsigned toPeriod(const unsigned freq) {
 
 namespace gambatte {
 
+DutyUnit::DutyUnit()
+: nextPosUpdate(COUNTER_DISABLED)
+, period(4096)
+, pos(0)
+, duty(0)
+, high(false)
+, enableEvents(true)
+{
+}
+
 void DutyUnit::updatePos(const unsigned long cc) {
 	if (cc >= nextPosUpdate) {
 		const unsigned long inc = (cc - nextPosUpdate) / period + 1;
@@ -96,15 +105,6 @@ void DutyUnit::nr4Change(const unsigned newNr4, const unsigned long cc) {
 	}
 }
 
-DutyUnit::DutyUnit() :
-nextPosUpdate(COUNTER_DISABLED),
-period(4096),
-pos(0),
-duty(0),
-high(false),
-enableEvents(true)
-{}
-
 void DutyUnit::reset() {
 	pos = 0;
 	high = toOutState(duty, pos);
@@ -119,7 +119,8 @@ void DutyUnit::saveState(SaveState::SPU::Duty &dstate, const unsigned long cc) {
 	dstate.pos = pos;
 }
 
-void DutyUnit::loadState(const SaveState::SPU::Duty &dstate, const unsigned nr1, const unsigned nr4, const unsigned long cc) {
+void DutyUnit::loadState(const SaveState::SPU::Duty &dstate,
+		const unsigned nr1, const unsigned nr4, const unsigned long cc) {
 	nextPosUpdate = std::max(dstate.nextPosUpdate, cc);
 	pos = dstate.pos & 7;
 	setDuty(nr1);
diff --git a/libgambatte/src/sound/duty_unit.h b/libgambatte/src/sound/duty_unit.h
index d0c61a02..eb8e871c 100644
--- a/libgambatte/src/sound/duty_unit.h
+++ b/libgambatte/src/sound/duty_unit.h
@@ -26,6 +26,25 @@
 namespace gambatte {
 
 class DutyUnit : public SoundUnit {
+public:
+	DutyUnit();
+	virtual void event();
+	bool isHighState() const { return high; }
+	void nr1Change(unsigned newNr1, unsigned long cc);
+	void nr3Change(unsigned newNr3, unsigned long cc);
+	void nr4Change(unsigned newNr4, unsigned long cc);
+	void reset();
+	void saveState(SaveState::SPU::Duty &dstate, unsigned long cc);
+	void loadState(const SaveState::SPU::Duty &dstate, unsigned nr1, unsigned nr4, unsigned long cc);
+	virtual void resetCounters(unsigned long oldCc);
+	void killCounter();
+	void reviveCounter(unsigned long cc);
+
+	//intended for use by SweepUnit only.
+	unsigned getFreq() const { return 2048 - (period >> 1); }
+	void setFreq(unsigned newFreq, unsigned long cc);
+
+private:
 	unsigned long nextPosUpdate;
 	unsigned short period;
 	unsigned char pos;
@@ -36,31 +55,13 @@ class DutyUnit : public SoundUnit {
 	void setCounter();
 	void setDuty(unsigned nr1);
 	void updatePos(unsigned long cc);
-
-public:
-	DutyUnit();
-	void event();
-	bool isHighState() const { return high; }
-	void nr1Change(unsigned newNr1, unsigned long cc);
-	void nr3Change(unsigned newNr3, unsigned long cc);
-	void nr4Change(unsigned newNr4, unsigned long cc);
-	void reset();
-	void saveState(SaveState::SPU::Duty &dstate, unsigned long cc);
-	void loadState(const SaveState::SPU::Duty &dstate, unsigned nr1, unsigned nr4, unsigned long cc);
-	void resetCounters(unsigned long oldCc);
-	void killCounter();
-	void reviveCounter(unsigned long cc);
-
-	//intended for use by SweepUnit only.
-	unsigned getFreq() const { return 2048 - (period >> 1); }
-	void setFreq(unsigned newFreq, unsigned long cc);
 };
 
 class DutyMasterDisabler : public MasterDisabler {
 	DutyUnit &dutyUnit;
 public:
 	DutyMasterDisabler(bool &m, DutyUnit &dutyUnit) : MasterDisabler(m), dutyUnit(dutyUnit) {}
-	void operator()() { MasterDisabler::operator()(); dutyUnit.killCounter(); }
+	virtual void operator()() { MasterDisabler::operator()(); dutyUnit.killCounter(); }
 };
 
 }