diff --git a/Machines/MSX/DiskROM.cpp b/Machines/MSX/DiskROM.cpp
index 2025098b9..af414657a 100644
--- a/Machines/MSX/DiskROM.cpp
+++ b/Machines/MSX/DiskROM.cpp
@@ -56,11 +56,12 @@ void DiskROM::run_for(HalfCycles half_cycles) {
 	controller_cycles_ %= 715909;
 }
 
-void DiskROM::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, int drive) {
+void DiskROM::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, size_t drive) {
 	if(!drives_[drive]) {
 		drives_[drive].reset(new Storage::Disk::Drive(8000000, 300, 2));
 		drives_[drive]->set_head(selected_head_);
 		if(drive == selected_drive_) set_drive(drives_[drive]);
+		drives_[drive]->set_activity_observer(observer_, drive_name(drive), true);
 	}
 	drives_[drive]->set_disk(disk);
 }
@@ -69,3 +70,16 @@ void DiskROM::set_head_load_request(bool head_load) {
 	// Magic!
 	set_head_loaded(head_load);
 }
+
+void DiskROM::set_activity_observer(Activity::Observer *observer) {
+	size_t c = 0;
+	observer_ = observer;
+	for(auto &drive: drives_) {
+		if(drive) drive->set_activity_observer(observer, drive_name(c), true);
+		++c;
+	}
+}
+
+std::string DiskROM::drive_name(size_t index) {
+	return "Drive " + std::to_string(index);
+}
diff --git a/Machines/MSX/DiskROM.hpp b/Machines/MSX/DiskROM.hpp
index bab03d380..b3f56d92d 100644
--- a/Machines/MSX/DiskROM.hpp
+++ b/Machines/MSX/DiskROM.hpp
@@ -11,9 +11,12 @@
 
 #include "ROMSlotHandler.hpp"
 
+#include "../../Activity/Source.hpp"
 #include "../../Components/1770/1770.hpp"
 
+#include <array>
 #include <cstdint>
+#include <string>
 #include <vector>
 
 namespace MSX {
@@ -26,17 +29,20 @@ class DiskROM: public ROMSlotHandler, public WD::WD1770 {
 		uint8_t read(uint16_t address) override;
 		void run_for(HalfCycles half_cycles) override;
 
-		void set_disk(std::shared_ptr<Storage::Disk::Disk> disk, int drive);
+		void set_disk(std::shared_ptr<Storage::Disk::Disk> disk, size_t drive);
+		void set_activity_observer(Activity::Observer *observer);
 
 	private:
 		const std::vector<uint8_t> &rom_;
 
 		long int controller_cycles_ = 0;
-		int selected_drive_ = 0;
+		size_t selected_drive_ = 0;
 		int selected_head_ = 0;
-		std::shared_ptr<Storage::Disk::Drive> drives_[4];
+		std::array<std::shared_ptr<Storage::Disk::Drive>, 2> drives_;
 
 		void set_head_load_request(bool head_load) override;
+		std::string drive_name(size_t index);
+		Activity::Observer *observer_ = nullptr;
 };
 
 }
diff --git a/Machines/MSX/MSX.cpp b/Machines/MSX/MSX.cpp
index 6b57f714c..daed39b44 100644
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@@ -30,6 +30,7 @@
 #include "../../Storage/Tape/Parsers/MSX.hpp"
 #include "../../Storage/Tape/Tape.hpp"
 
+#include "../../Activity/Source.hpp"
 #include "../CRTMachine.hpp"
 #include "../ConfigurationTarget.hpp"
 #include "../KeyboardMachine.hpp"
@@ -87,7 +88,8 @@ class ConcreteMachine:
 	public KeyboardMachine::Machine,
 	public Configurable::Device,
 	public MemoryMap,
-	public Sleeper::SleepObserver {
+	public Sleeper::SleepObserver,
+	public Activity::Source {
 	public:
 		ConcreteMachine():
 			z80_(*this),
@@ -200,12 +202,14 @@ class ConcreteMachine:
 			}
 
 			if(!media.disks.empty()) {
-				DiskROM *disk_rom = dynamic_cast<DiskROM *>(memory_slots_[2].handler.get());
-				int drive = 0;
-				for(auto &disk : media.disks) {
-					disk_rom->set_disk(disk, drive);
-					drive++;
-					if(drive == 2) break;
+				DiskROM *disk_rom = get_disk_rom();
+				if(disk_rom) {
+					size_t drive = 0;
+					for(auto &disk : media.disks) {
+						disk_rom->set_disk(disk, drive);
+						drive++;
+						if(drive == 2) break;
+					}
 				}
 			}
 
@@ -556,7 +560,18 @@ class ConcreteMachine:
 			set_use_fast_tape();
 		}
 
+		// MARK: - Activity::Source
+		void set_activity_observer(Activity::Observer *observer) override {
+			DiskROM *disk_rom = get_disk_rom();
+			if(disk_rom) {
+				disk_rom->set_activity_observer(observer);
+			}
+		}
+
 	private:
+		DiskROM *get_disk_rom() {
+			return dynamic_cast<DiskROM *>(memory_slots_[2].handler.get());
+		}
 		void update_audio() {
 			speaker_.run_for(audio_queue_, time_since_ay_update_.divide_cycles(Cycles(2)));
 		}
diff --git a/Machines/Oric/Microdisc.cpp b/Machines/Oric/Microdisc.cpp
index a19966c30..e040ce5fb 100644
--- a/Machines/Oric/Microdisc.cpp
+++ b/Machines/Oric/Microdisc.cpp
@@ -26,7 +26,7 @@ void Microdisc::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, size_t drive
 	if(!drives_[drive]) {
 		drives_[drive].reset(new Storage::Disk::Drive(8000000, 300, 2));
 		if(drive == selected_drive_) set_drive(drives_[drive]);
-		drives_[drive]->set_activity_observer(observer_, "Drive" + std::to_string(drive), false);
+		drives_[drive]->set_activity_observer(observer_, drive_name(drive), false);
 	}
 	drives_[drive]->set_disk(disk);
 }
@@ -132,7 +132,11 @@ void Microdisc::set_activity_observer(Activity::Observer *observer) {
 	}
 	size_t c = 0;
 	for(auto &drive : drives_) {
-		if(drive) drive->set_activity_observer(observer, "Drive" + std::to_string(c), false);
+		if(drive) drive->set_activity_observer(observer, drive_name(c), false);
 		++c;
 	}
 }
+
+std::string Microdisc::drive_name(size_t index) {
+	return "Drive " + std::to_string(index);
+}
diff --git a/Machines/Oric/Microdisc.hpp b/Machines/Oric/Microdisc.hpp
index f8e847ff3..862e7ec8e 100644
--- a/Machines/Oric/Microdisc.hpp
+++ b/Machines/Oric/Microdisc.hpp
@@ -57,6 +57,8 @@ class Microdisc: public WD::WD1770 {
 		Delegate *delegate_ = nullptr;
 		uint8_t last_control_ = 0;
 		Activity::Observer *observer_ = nullptr;
+
+		std::string drive_name(size_t index);
 };
 
 }