diff --git a/Machines/MSX/MSX.cpp b/Machines/MSX/MSX.cpp
index 9298d35cd..fd5b9e972 100644
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@@ -633,9 +633,11 @@ class ConcreteMachine:
 									break;
 								}
 
-								// TODO: Propagate to all handlers.
-
 								// Apply to RAM.
+								//
+								// On a real MSX this may also affect other slots.
+								// I've not yet needed it to propagate further, so
+								// have not implemented any onward route.
 								const uint16_t region = uint16_t((port - 0xfc) << 14);
 								const size_t base = size_t(*cycle.value) << 14;
 								if(base < RAMSize) {
diff --git a/Machines/MSX/MemorySlotHandler.hpp b/Machines/MSX/MemorySlotHandler.hpp
index cc046e78c..874b76b4f 100644
--- a/Machines/MSX/MemorySlotHandler.hpp
+++ b/Machines/MSX/MemorySlotHandler.hpp
@@ -129,10 +129,6 @@ class MemorySlotHandler {
 		/*! Seeks the result of a read at @c address; this is used only if the area is unmapped. */
 		virtual uint8_t read([[maybe_unused]] uint16_t address) { return 0xff; }
 
-		/// Sets the value most-recently written to one of the standard
-		/// memory mapping ports, FC–FF.
-		virtual void apply_mapping([[maybe_unused]] uint8_t port, [[maybe_unused]] uint8_t value) {}
-
 		/*! @returns The probability that this handler is correct for the data it owns. */
 		float get_confidence() {
 			return confidence_counter_.get_confidence();