diff --git a/repos/os/include/os/alarm.h b/repos/os/include/os/alarm.h
index 43f51a6279..b2c1f02063 100644
--- a/repos/os/include/os/alarm.h
+++ b/repos/os/include/os/alarm.h
@@ -52,7 +52,7 @@ namespace Genode {
 			 * return value is 'true' and the alarm is periodically scheduled,
 			 * the alarm is scheduled again.
 			 */
-			virtual bool on_alarm() { return false; }
+			virtual bool on_alarm(unsigned) { return false; }
 
 		public:
 
diff --git a/repos/os/include/os/timed_semaphore.h b/repos/os/include/os/timed_semaphore.h
index 45f886d8e1..088e5f1b89 100644
--- a/repos/os/include/os/timed_semaphore.h
+++ b/repos/os/include/os/timed_semaphore.h
@@ -155,7 +155,7 @@ namespace Genode {
 
 				protected:
 
-					bool on_alarm()
+					bool on_alarm(unsigned) override
 					{
 						/* Abort blocking operation */
 						_triggered = _sem->_abort(_element);
diff --git a/repos/os/src/drivers/timer/include/timer_session_component.h b/repos/os/src/drivers/timer/include/timer_session_component.h
index d97843f063..563efdd66a 100644
--- a/repos/os/src/drivers/timer/include/timer_session_component.h
+++ b/repos/os/src/drivers/timer/include/timer_session_component.h
@@ -122,9 +122,9 @@ namespace Timer {
 			 *
 			 * This function gets called by the 'Alarm_scheduler' thread.
 			 */
-			bool on_alarm()
+			bool on_alarm (unsigned cnt) override
 			{
-				Signal_transmitter(_sigh).submit();
+				Signal_transmitter(_sigh).submit(cnt);
 
 				return _periodic;
 			}
diff --git a/repos/os/src/lib/alarm/alarm.cc b/repos/os/src/lib/alarm/alarm.cc
index 263ae46f58..5906e49ffb 100644
--- a/repos/os/src/lib/alarm/alarm.cc
+++ b/repos/os/src/lib/alarm/alarm.cc
@@ -113,7 +113,7 @@ void Alarm_scheduler::handle(Alarm::Time curr_time)
 	while ((curr = _get_pending_alarm())) {
 
 		/* do not reschedule if alarm function returns 0 */
-		bool reschedule = curr->on_alarm();
+		bool reschedule = curr->on_alarm(1);
 
 		if (reschedule) {
 
diff --git a/repos/os/src/lib/dde_kit/timer.cc b/repos/os/src/lib/dde_kit/timer.cc
index 3c2119302d..1208b39f1e 100644
--- a/repos/os/src/lib/dde_kit/timer.cc
+++ b/repos/os/src/lib/dde_kit/timer.cc
@@ -134,7 +134,7 @@ class dde_kit_timer : public Alarm, public List<dde_kit_timer>::Element
 
 	protected:
 
-		bool on_alarm()
+		bool on_alarm(unsigned) override
 		{
 			/* if timer is really pending, call registered handler function */
 			if (_pending) {
diff --git a/repos/os/src/test/alarm/main.cc b/repos/os/src/test/alarm/main.cc
index 9b6d2d83f9..0be161beb6 100644
--- a/repos/os/src/test/alarm/main.cc
+++ b/repos/os/src/test/alarm/main.cc
@@ -70,7 +70,7 @@ class One_shot_alarm : public Alarm
 
 	protected:
 
-		bool on_alarm()
+		bool on_alarm(unsigned) override
 		{
 			printf("one-shot alarm %s triggered\n", _name);
 			return false;
@@ -95,7 +95,7 @@ class Periodic_alarm : public Alarm
 
 	protected:
 
-		bool on_alarm()
+		bool on_alarm(unsigned) override
 		{
 			printf("periodic alarm %s triggered\n", _name);
 			return true;
diff --git a/repos/ports/src/app/netperf/timer.cc b/repos/ports/src/app/netperf/timer.cc
index d3c6bf1e3f..d9e354994f 100644
--- a/repos/ports/src/app/netperf/timer.cc
+++ b/repos/ports/src/app/netperf/timer.cc
@@ -71,7 +71,7 @@ class One_shot : public Alarm
 
 	protected:
 
-		bool on_alarm()
+		bool on_alarm(unsigned) override
 		{
 			times_up = 1;
 			return false;
diff --git a/repos/ports/src/noux/main.cc b/repos/ports/src/noux/main.cc
index 6cfdf73e09..2fc89d5122 100644
--- a/repos/ports/src/noux/main.cc
+++ b/repos/ports/src/noux/main.cc
@@ -116,7 +116,8 @@ namespace Noux {
 			void discard() { _scheduler->discard(this); }
 
 		protected:
-			bool on_alarm()
+
+			bool on_alarm(unsigned) override
 			{
 				_state->timed_out = true;
 				_blocker->unlock();
diff --git a/repos/ports/src/virtualbox/sup.cc b/repos/ports/src/virtualbox/sup.cc
index 5a585511c8..bd35cc59cc 100644
--- a/repos/ports/src/virtualbox/sup.cc
+++ b/repos/ports/src/virtualbox/sup.cc
@@ -44,7 +44,7 @@ PSUPGLOBALINFOPAGE g_pSUPGlobalInfoPage;
 
 class Periodic_GIP : public Genode::Alarm {
 
-	bool on_alarm()
+	bool on_alarm(unsigned) override
 	{
 		/**
 		 * We're using rdtsc here since timer_session->elapsed_ms produces