diff --git a/Machines/Apple/AppleIIgs/AppleIIgs.cpp b/Machines/Apple/AppleIIgs/AppleIIgs.cpp
index 1ad32d3ed..7562ad6ec 100644
--- a/Machines/Apple/AppleIIgs/AppleIIgs.cpp
+++ b/Machines/Apple/AppleIIgs/AppleIIgs.cpp
@@ -8,6 +8,7 @@
 
 #include "AppleIIgs.hpp"
 
+#include "../../../Activity/Source.hpp"
 #include "../../MachineTypes.hpp"
 #include "../../../Processors/65816/65816.hpp"
 
@@ -42,6 +43,7 @@ namespace Apple {
 namespace IIgs {
 
 class ConcreteMachine:
+	public Activity::Source,
 	public Apple::IIgs::Machine,
 	public MachineTypes::AudioProducer,
 	public MachineTypes::MediaTarget,
@@ -165,6 +167,12 @@ class ConcreteMachine:
 			return true;
 		}
 
+		// MARK: Activity::Source
+		void set_activity_observer(Activity::Observer *observer) final {
+			drives_[0].set_activity_observer(observer, "First 3.5\" Drive", true);
+			drives_[1].set_activity_observer(observer, "Second 3.5\" Drive", true);
+		}
+
 		// MARK: BusHandler.
 		forceinline Cycles perform_bus_operation(const CPU::WDC65816::BusOperation operation, const uint32_t address, uint8_t *const value) {
 			const auto &region = MemoryMapRegion(memory_, address);