diff --git a/Machines/Apple/Macintosh/Macintosh.cpp b/Machines/Apple/Macintosh/Macintosh.cpp
index e0053ccb1..4db65ca4e 100644
--- a/Machines/Apple/Macintosh/Macintosh.cpp
+++ b/Machines/Apple/Macintosh/Macintosh.cpp
@@ -500,6 +500,10 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 		// MARK: - Activity Source
 		void set_activity_observer(Activity::Observer *observer) override {
 			iwm_->set_activity_observer(observer);
+
+			if(model == Analyser::Static::Macintosh::Target::Model::MacPlus) {
+				scsi_bus_.set_activity_observer(observer);
+			}
 		}
 
 	private:
diff --git a/Storage/MassStorage/SCSI/SCSI.cpp b/Storage/MassStorage/SCSI/SCSI.cpp
index 446f14875..da3667b75 100644
--- a/Storage/MassStorage/SCSI/SCSI.cpp
+++ b/Storage/MassStorage/SCSI/SCSI.cpp
@@ -44,6 +44,10 @@ void Bus::set_device_output(size_t device, BusState output) {
 	}
 	if(state_ == previous_state) return;
 
+	if(activity_observer_ && (state_^previous_state)&SCSI::Line::Busy) {
+		activity_observer_->set_led_status("SCSI", state_&SCSI::Line::Busy);
+	}
+
 //	printf("SCSI bus: %02x %c%c%c%c%c%c%c%c%c%c\n",
 //		state_ & 0xff,
 //		(state_ & Line::Parity) ? 'p' : '-',
@@ -64,6 +68,11 @@ void Bus::set_device_output(size_t device, BusState output) {
 	if(was_asleep) update_clocking_observer();
 }
 
+void Bus::set_activity_observer(Activity::Observer *observer) {
+	activity_observer_ = observer;
+	activity_observer_->register_led("SCSI");
+}
+
 BusState Bus::get_state() {
 	return state_;
 }
diff --git a/Storage/MassStorage/SCSI/SCSI.hpp b/Storage/MassStorage/SCSI/SCSI.hpp
index ddc8703d6..c1502fa1f 100644
--- a/Storage/MassStorage/SCSI/SCSI.hpp
+++ b/Storage/MassStorage/SCSI/SCSI.hpp
@@ -15,6 +15,7 @@
 
 #include "../../../ClockReceiver/ClockReceiver.hpp"
 #include "../../../ClockReceiver/ClockingHintSource.hpp"
+#include "../../../Activity/Source.hpp"
 
 namespace SCSI {
 
@@ -92,7 +93,7 @@ constexpr double CableSkew			= ns(10.0);
 #undef ns
 #undef us
 
-class Bus: public ClockingHint::Source {
+class Bus: public ClockingHint::Source, public Activity::Source {
 	public:
 		Bus(HalfCycles clock_rate);
 
@@ -137,9 +138,12 @@ class Bus: public ClockingHint::Source {
 		*/
 		void update_observers();
 
-		/// As per ClockingHint::Source.
+		// As per ClockingHint::Source.
 		ClockingHint::Preference preferred_clocking() final;
 
+		// Fulfilling public Activity::Source.
+		void set_activity_observer(Activity::Observer *observer) final;
+
 	private:
 		HalfCycles time_in_state_;
 		double cycles_to_time_ = 1.0;
@@ -149,6 +153,8 @@ class Bus: public ClockingHint::Source {
 		std::vector<BusState> device_states_;
 		BusState state_ = DefaultBusState;
 		std::vector<Observer *> observers_;
+
+		Activity::Observer *activity_observer_ = nullptr;
 };
 
 }