diff --git a/Analyser/Static/AmstradCPC/StaticAnalyser.cpp b/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
index bb6479cc4..39d5e2148 100644
--- a/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
+++ b/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
@@ -16,6 +16,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <optional>
 #include <unordered_set>
 
 namespace {
diff --git a/Machines/Acorn/Archimedes/CMOSRAM.hpp b/Machines/Acorn/Archimedes/CMOSRAM.hpp
index 561f68528..741cf8131 100644
--- a/Machines/Acorn/Archimedes/CMOSRAM.hpp
+++ b/Machines/Acorn/Archimedes/CMOSRAM.hpp
@@ -12,6 +12,7 @@
 #include "Outputs/Log.hpp"
 
 #include <array>
+#include <optional>
 
 namespace Archimedes {
 
diff --git a/Machines/Commodore/Plus4/Plus4.cpp b/Machines/Commodore/Plus4/Plus4.cpp
index a3c7cdc93..6b655f5ec 100644
--- a/Machines/Commodore/Plus4/Plus4.cpp
+++ b/Machines/Commodore/Plus4/Plus4.cpp
@@ -34,6 +34,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <optional>
 #include <vector>
 
 using namespace Commodore;
diff --git a/Machines/Commodore/Vic-20/Vic20.cpp b/Machines/Commodore/Vic-20/Vic20.cpp
index e30696c3c..561a5b399 100644
--- a/Machines/Commodore/Vic-20/Vic20.cpp
+++ b/Machines/Commodore/Vic-20/Vic20.cpp
@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <array>
 #include <cstdint>
+#include <optional>
 
 namespace {
 using Logger = Log::Logger<Log::Source::Vic20>;
diff --git a/Machines/Utility/ROMCatalogue.cpp b/Machines/Utility/ROMCatalogue.cpp
index d5b2355fb..51b3e3290 100644
--- a/Machines/Utility/ROMCatalogue.cpp
+++ b/Machines/Utility/ROMCatalogue.cpp
@@ -13,6 +13,7 @@
 #include <cstdlib>
 #include <iomanip>
 #include <locale>
+#include <optional>
 #include <sstream>
 
 using namespace ROM;
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm
index 1f3fb856b..8f9d3c7e3 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSROMFetcher.mm	
@@ -13,6 +13,7 @@
 #import "NSData+StdVector.h"
 #import "NSData+CRC32.h"
 
+#include <optional>
 #include <string>
 
 namespace {
diff --git a/Outputs/CRT/CRT.cpp b/Outputs/CRT/CRT.cpp
index 58fd60b02..401ba969a 100644
--- a/Outputs/CRT/CRT.cpp
+++ b/Outputs/CRT/CRT.cpp
@@ -14,6 +14,7 @@
 #include <cassert>
 #include <cmath>
 #include <cstdarg>
+#include <optional>
 
 using namespace Outputs::CRT;
 using Logger = Log::Logger<Log::Source::CRT>;
diff --git a/Outputs/OpenGL/ScanTarget.hpp b/Outputs/OpenGL/ScanTarget.hpp
index c7c23efd3..b3f2e9ca6 100644
--- a/Outputs/OpenGL/ScanTarget.hpp
+++ b/Outputs/OpenGL/ScanTarget.hpp
@@ -24,6 +24,7 @@
 #include <chrono>
 #include <list>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
diff --git a/Storage/Data/ZX8081.cpp b/Storage/Data/ZX8081.cpp
index 92c5a911c..6c32b46fe 100644
--- a/Storage/Data/ZX8081.cpp
+++ b/Storage/Data/ZX8081.cpp
@@ -8,6 +8,8 @@
 
 #include "ZX8081.hpp"
 
+#include <optional>
+
 using namespace Storage::Data::ZX8081;
 
 namespace {
diff --git a/Storage/Disk/Encodings/MFM/Encoder.cpp b/Storage/Disk/Encodings/MFM/Encoder.cpp
index cf77210d5..dcfeb0282 100644
--- a/Storage/Disk/Encodings/MFM/Encoder.cpp
+++ b/Storage/Disk/Encodings/MFM/Encoder.cpp
@@ -14,7 +14,7 @@
 #include "Numeric/BitSpread.hpp"
 
 #include <cassert>
-#include <set>
+#include <optional>
 
 using namespace Storage::Encodings::MFM;
 
diff --git a/Storage/Disk/Parsers/FAT.cpp b/Storage/Disk/Parsers/FAT.cpp
index 3f53e71f5..919cf7177 100644
--- a/Storage/Disk/Parsers/FAT.cpp
+++ b/Storage/Disk/Parsers/FAT.cpp
@@ -12,6 +12,7 @@
 
 #include <algorithm>
 #include <iostream>
+#include <optional>
 
 using namespace Storage::Disk;
 
diff --git a/Storage/Tape/Parsers/ZX8081.hpp b/Storage/Tape/Parsers/ZX8081.hpp
index 20708f5a6..9bfc5c4d8 100644
--- a/Storage/Tape/Parsers/ZX8081.hpp
+++ b/Storage/Tape/Parsers/ZX8081.hpp
@@ -12,6 +12,7 @@
 
 #include "Storage/Data/ZX8081.hpp"
 
+#include <optional>
 #include <string>
 #include <vector>
 #include <cstdint>