diff --git a/src/network/core/http_winhttp.cpp b/src/network/core/http_winhttp.cpp
index c37711119a..df57fc138a 100644
--- a/src/network/core/http_winhttp.cpp
+++ b/src/network/core/http_winhttp.cpp
@@ -67,7 +67,7 @@ static std::string GetLastErrorAsString()
 	DWORD error_code = GetLastError();
 
 	if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_FROM_HMODULE | FORMAT_MESSAGE_IGNORE_INSERTS, GetModuleHandleA("winhttp.dll"), error_code,
-		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), NULL) == 0) {
+		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), nullptr) == 0) {
 		return fmt::format("unknown error {}", error_code);
 	}
 
diff --git a/src/network/core/os_abstraction.cpp b/src/network/core/os_abstraction.cpp
index 8da0a3f3d0..792ee8b2f4 100644
--- a/src/network/core/os_abstraction.cpp
+++ b/src/network/core/os_abstraction.cpp
@@ -81,8 +81,8 @@ const std::string &NetworkError::AsString() const
 	if (this->message.empty()) {
 #if defined(_WIN32)
 		char buffer[512];
-		if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, this->error,
-			MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), NULL) == 0) {
+		if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr, this->error,
+			MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), nullptr) == 0) {
 			this->message.assign(fmt::format("Unknown error {}", this->error));
 		} else {
 			this->message.assign(buffer);
diff --git a/src/video/cocoa/cocoa_v.mm b/src/video/cocoa/cocoa_v.mm
index 2a9ae02424..0be6745b0c 100644
--- a/src/video/cocoa/cocoa_v.mm
+++ b/src/video/cocoa/cocoa_v.mm
@@ -664,7 +664,7 @@ void VideoDriver_CocoaQuartz::AllocateBackingStore(bool)
 		kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host
 	);
 
-	assert(this->cgcontext != NULL);
+	assert(this->cgcontext != nullptr);
 	CGContextSetShouldAntialias(this->cgcontext, FALSE);
 	CGContextSetAllowsAntialiasing(this->cgcontext, FALSE);
 	CGContextSetInterpolationQuality(this->cgcontext, kCGInterpolationNone);
diff --git a/src/video/cocoa/cocoa_wnd.mm b/src/video/cocoa/cocoa_wnd.mm
index 52823a7a6c..f6957ff6ef 100644
--- a/src/video/cocoa/cocoa_wnd.mm
+++ b/src/video/cocoa/cocoa_wnd.mm
@@ -929,16 +929,16 @@ void CocoaDialog(const char *title, const char *message, const char *buttonLabel
 
 	NSString *s = [ aString isKindOfClass:[ NSAttributedString class ] ] ? [ aString string ] : (NSString *)aString;
 
-	const char *insert_point = NULL;
-	const char *replace_range = NULL;
+	const char *insert_point = nullptr;
+	const char *replace_range = nullptr;
 	if (replacementRange.location != NSNotFound) {
 		/* Calculate the part to be replaced. */
 		insert_point = Utf8AdvanceByUtf16Units(_focused_window->GetFocusedTextbuf()->GetText(), replacementRange.location);
 		replace_range = Utf8AdvanceByUtf16Units(insert_point, replacementRange.length);
 	}
 
-	HandleTextInput(NULL, true);
-	HandleTextInput([ s UTF8String ], false, NULL, insert_point, replace_range);
+	HandleTextInput(nullptr, true);
+	HandleTextInput([ s UTF8String ], false, nullptr, insert_point, replace_range);
 }
 
 /** Insert the given text at the caret. */
@@ -955,9 +955,9 @@ void CocoaDialog(const char *title, const char *message, const char *buttonLabel
 	NSString *s = [ aString isKindOfClass:[ NSAttributedString class ] ] ? [ aString string ] : (NSString *)aString;
 
 	const char *utf8 = [ s UTF8String ];
-	if (utf8 != NULL) {
-		const char *insert_point = NULL;
-		const char *replace_range = NULL;
+	if (utf8 != nullptr) {
+		const char *insert_point = nullptr;
+		const char *replace_range = nullptr;
 		if (replacementRange.location != NSNotFound) {
 			/* Calculate the part to be replaced. */
 			NSRange marked = [ self markedRange ];
diff --git a/src/video/win32_v.cpp b/src/video/win32_v.cpp
index cf7a909451..833f4bf72d 100644
--- a/src/video/win32_v.cpp
+++ b/src/video/win32_v.cpp
@@ -275,7 +275,7 @@ static bool DrawIMECompositionString()
 static void SetCompositionPos(HWND hwnd)
 {
 	HIMC hIMC = ImmGetContext(hwnd);
-	if (hIMC != NULL) {
+	if (hIMC != nullptr) {
 		COMPOSITIONFORM cf;
 		cf.dwStyle = CFS_POINT;
 
@@ -297,7 +297,7 @@ static void SetCompositionPos(HWND hwnd)
 static void SetCandidatePos(HWND hwnd)
 {
 	HIMC hIMC = ImmGetContext(hwnd);
-	if (hIMC != NULL) {
+	if (hIMC != nullptr) {
 		CANDIDATEFORM cf;
 		cf.dwIndex = 0;
 		cf.dwStyle = CFS_EXCLUDE;
@@ -332,7 +332,7 @@ static LRESULT HandleIMEComposition(HWND hwnd, WPARAM wParam, LPARAM lParam)
 {
 	HIMC hIMC = ImmGetContext(hwnd);
 
-	if (hIMC != NULL) {
+	if (hIMC != nullptr) {
 		if (lParam & GCS_RESULTSTR) {
 			/* Read result string from the IME. */
 			LONG len = ImmGetCompositionString(hIMC, GCS_RESULTSTR, nullptr, 0); // Length is always in bytes, even in UNICODE build.
@@ -391,7 +391,7 @@ static LRESULT HandleIMEComposition(HWND hwnd, WPARAM wParam, LPARAM lParam)
 static void CancelIMEComposition(HWND hwnd)
 {
 	HIMC hIMC = ImmGetContext(hwnd);
-	if (hIMC != NULL) ImmNotifyIME(hIMC, NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+	if (hIMC != nullptr) ImmNotifyIME(hIMC, NI_COMPOSITIONSTR, CPS_CANCEL, 0);
 	ImmReleaseContext(hwnd, hIMC);
 	/* Clear any marked string from the current edit box. */
 	HandleTextInput(nullptr, true);
@@ -688,7 +688,7 @@ LRESULT CALLBACK WndProcGdi(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 			/* Resize the window to match the new DPI setting. */
 			RECT *prcNewWindow = (RECT *)lParam;
 			SetWindowPos(hwnd,
-				NULL,
+				nullptr,
 				prcNewWindow->left,
 				prcNewWindow->top,
 				prcNewWindow->right - prcNewWindow->left,