diff --git a/src/network/core/http_winhttp.cpp b/src/network/core/http_winhttp.cpp
index 9d365f6d17..8acab0a5a3 100644
--- a/src/network/core/http_winhttp.cpp
+++ b/src/network/core/http_winhttp.cpp
@@ -73,15 +73,16 @@ NetworkHTTPRequest::NetworkHTTPRequest(const std::wstring &uri, HTTPCallback *ca
 
 static std::string GetLastErrorAsString()
 {
-	char buffer[512];
+	wchar_t buffer[512];
+
 	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), nullptr) == 0) {
+	if (FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_FROM_HMODULE | FORMAT_MESSAGE_IGNORE_INSERTS, GetModuleHandle(L"winhttp.dll"), error_code,
+		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, lengthof(buffer), nullptr) == 0) {
 		return fmt::format("unknown error {}", error_code);
 	}
 
-	return buffer;
+	return FS2OTTD(buffer);
 }
 
 /**
diff --git a/src/network/core/os_abstraction.cpp b/src/network/core/os_abstraction.cpp
index 62bec62852..97647a4165 100644
--- a/src/network/core/os_abstraction.cpp
+++ b/src/network/core/os_abstraction.cpp
@@ -81,12 +81,12 @@ 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, nullptr, this->error,
-			MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), nullptr) == 0) {
+		wchar_t buffer[512];
+		if (FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr, this->error,
+			MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, lengthof(buffer), nullptr) == 0) {
 			this->message.assign(fmt::format("Unknown error {}", this->error));
 		} else {
-			this->message.assign(buffer);
+			this->message.assign(FS2OTTD(buffer));
 		}
 #else
 		/* Make strerror thread safe by locking access to it. There is a thread safe strerror_r, however
diff --git a/src/os/windows/library_loader_win.cpp b/src/os/windows/library_loader_win.cpp
index 0281b0ab23..eea8f061f9 100644
--- a/src/os/windows/library_loader_win.cpp
+++ b/src/os/windows/library_loader_win.cpp
@@ -20,13 +20,13 @@ static std::string GetLoadError()
 {
 	auto error_code = GetLastError();
 
-	char buffer[512];
-	if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr, error_code,
-		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), nullptr) == 0) {
+	wchar_t buffer[512];
+	if (FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr, error_code,
+		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, lengthof(buffer), nullptr) == 0) {
 		return fmt::format("Unknown error {}", error_code);
 	}
 
-	return buffer;
+	return FS2OTTD(buffer);
 }
 
 void *LibraryLoader::OpenLibrary(const std::string &filename)