diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index cb265c8f6..dec96b36d 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -339,6 +339,7 @@
 		4BB0A65E204500A900FB3688 /* StaticAnalyser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B7A90EC20410A85008514A2 /* StaticAnalyser.cpp */; };
 		4BB17D4E1ED7909F00ABD1E1 /* tests.expected.json in Resources */ = {isa = PBXBuildFile; fileRef = 4BB17D4C1ED7909F00ABD1E1 /* tests.expected.json */; };
 		4BB17D4F1ED7909F00ABD1E1 /* tests.in.json in Resources */ = {isa = PBXBuildFile; fileRef = 4BB17D4D1ED7909F00ABD1E1 /* tests.in.json */; };
+		4BB1CBB522E5215B0030C002 /* ROMImages in Resources */ = {isa = PBXBuildFile; fileRef = 4BC9DF441D044FCA00F44158 /* ROMImages */; };
 		4BB244D522AABAF600BE20E5 /* z8530.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BB244D322AABAF500BE20E5 /* z8530.cpp */; };
 		4BB244D622AABAF600BE20E5 /* z8530.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BB244D322AABAF500BE20E5 /* z8530.cpp */; };
 		4BB298F11B587D8400A49093 /*  start in Resources */ = {isa = PBXBuildFile; fileRef = 4BB297E51B587D8300A49093 /*  start */; };
@@ -633,7 +634,6 @@
 		4BC76E691C98E31700E6EF73 /* FIRFilter.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC76E671C98E31700E6EF73 /* FIRFilter.cpp */; };
 		4BC76E6B1C98F43700E6EF73 /* Accelerate.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 4BC76E6A1C98F43700E6EF73 /* Accelerate.framework */; };
 		4BC91B831D1F160E00884B76 /* CommodoreTAP.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC91B811D1F160E00884B76 /* CommodoreTAP.cpp */; };
-		4BC9DF451D044FCA00F44158 /* ROMImages in Resources */ = {isa = PBXBuildFile; fileRef = 4BC9DF441D044FCA00F44158 /* ROMImages */; };
 		4BC9DF4F1D04691600F44158 /* 6560.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BC9DF4D1D04691600F44158 /* 6560.cpp */; };
 		4BC9E1EE1D23449A003FCEE4 /* 6502InterruptTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4BC9E1ED1D23449A003FCEE4 /* 6502InterruptTests.swift */; };
 		4BCA6CC81D9DD9F000C2D7B2 /* CommodoreROM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4BCA6CC61D9DD9F000C2D7B2 /* CommodoreROM.cpp */; };
@@ -3555,9 +3555,9 @@
 				4BB73EAC1B587A5100552FC2 /* MainMenu.xib in Resources */,
 				4B8FE21D1DA19D5F0090D3CE /* QuickLoadCompositeOptions.xib in Resources */,
 				4B79E4461E3AF38600141F11 /* floppy525.png in Resources */,
-				4BC9DF451D044FCA00F44158 /* ROMImages in Resources */,
 				4BEEE6BD20DC72EB003723BF /* CompositeOptions.xib in Resources */,
 				4B1497981EE4B97F00CE2596 /* ZX8081Options.xib in Resources */,
+				4BB1CBB522E5215B0030C002 /* ROMImages in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm
index c2077baef..1aa0fab1f 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
@@ -96,7 +96,8 @@ struct ActivityObserver: public Activity::Observer {
 		_analyser = result;
 
 		Machine::Error error;
-		_machine.reset(Machine::MachineForTargets(_analyser.targets, CSROMFetcher(), error));
+		std::vector<ROMMachine::ROM> missing_roms;
+		_machine.reset(Machine::MachineForTargets(_analyser.targets, CSROMFetcher(&missing_roms), error));
 		if(!_machine) return nil;
 
 		_inputMode =
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.hpp b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.hpp
index 28958b535..f1d039ade 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.hpp	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.hpp	
@@ -8,4 +8,4 @@
 
 #include "ROMMachine.hpp"
 
-ROMMachine::ROMFetcher CSROMFetcher();
+ROMMachine::ROMFetcher CSROMFetcher(std::vector<ROMMachine::ROM> *missing_roms = nullptr);
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm
index 87c1f5f85..9345040c0 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm	
@@ -14,8 +14,8 @@
 
 #include <string>
 
-ROMMachine::ROMFetcher CSROMFetcher() {
-	return [] (const std::string &machine, const std::vector<ROMMachine::ROM> &roms) -> std::vector<std::unique_ptr<std::vector<std::uint8_t>>> {
+ROMMachine::ROMFetcher CSROMFetcher(std::vector<ROMMachine::ROM> *missing_roms) {
+	return [missing_roms] (const std::string &machine, const std::vector<ROMMachine::ROM> &roms) -> std::vector<std::unique_ptr<std::vector<std::uint8_t>>> {
 		NSString *const subdirectory = [@"ROMImages/" stringByAppendingString:[NSString stringWithUTF8String:machine.c_str()]];
 		NSArray<NSURL *> *const supportURLs = [[NSFileManager defaultManager] URLsForDirectory:NSApplicationSupportDirectory inDomains:NSUserDomainMask];
 
@@ -39,9 +39,14 @@ ROMMachine::ROMFetcher CSROMFetcher() {
 					subdirectory:subdirectory];
 			}
 
-			// Store an appropriate result.
-			if(!fileData)
+			// Store an appropriate result, accumulating a list of the missing if requested.
+			if(!fileData) {
 				results.emplace_back(nullptr);
+
+				if(missing_roms) {
+					missing_roms->push_back(rom);
+				}
+			}
 			else {
 				std::unique_ptr<std::vector<std::uint8_t>> data(new std::vector<std::uint8_t>);
 				*data = fileData.stdVector8;