diff --git a/source/third_party/cppformat/format.cpp b/source/third_party/cppformat/format.cpp
index ce9b90dac0..4aee869355 100644
--- a/source/third_party/cppformat/format.cpp
+++ b/source/third_party/cppformat/format.cpp
@@ -1,3 +1,8 @@
+/*
+ * Slightly modified version of cppformat, by Wildfire Games, for 0 A.D.
+ * Based on cppformat v0.11.0 from https://github.com/cppformat/cppformat
+ */
+
 /*
  Formatting library for C++
 
@@ -54,7 +59,7 @@ using fmt::LongLong;
 using fmt::ULongLong;
 using fmt::internal::Arg;
 
-#if _MSC_VER
+#ifdef _MSC_VER
 # pragma warning(push)
 # pragma warning(disable: 4127) // conditional expression is constant
 #endif
@@ -430,12 +435,12 @@ int fmt::internal::safe_strerror(
   if (message == buffer && strlen(buffer) == buffer_size - 1)
     result = ERANGE;
   buffer = message;
-#elif __MINGW32__
+#elif defined(__MINGW32__)
   errno = 0;
   (void)buffer_size;
   buffer = strerror(error_code);
   result = errno;
-#elif _WIN32
+#elif defined(_WIN32)
   result = strerror_s(buffer, buffer_size, error_code);
   // If the buffer is full then the message is probably truncated.
   if (result == 0 && std::strlen(buffer) == buffer_size - 1)
@@ -692,7 +697,7 @@ void fmt::BasicWriter<Char>::write_double(T value, const FormatSpec &spec) {
   Char fill = static_cast<Char>(spec.fill());
   for (;;) {
     std::size_t size = buffer_.capacity() - offset;
-#if _MSC_VER
+#ifdef _MSC_VER
     // MSVC's vsnprintf_s doesn't work with zero size, so reserve
     // space for at least one extra character to make the size non-zero.
     // Note that the buffer's capacity will increase by more than 1.
@@ -1299,6 +1304,6 @@ template void fmt::internal::PrintfFormatter<wchar_t>::format(
     BasicWriter<wchar_t> &writer, BasicStringRef<wchar_t> format,
     const ArgList &args);
 
-#if _MSC_VER
+#ifdef _MSC_VER
 # pragma warning(pop)
 #endif
diff --git a/source/third_party/cppformat/format.h b/source/third_party/cppformat/format.h
index 94a174755b..5a139acc48 100644
--- a/source/third_party/cppformat/format.h
+++ b/source/third_party/cppformat/format.h
@@ -1,3 +1,8 @@
+/*
+ * Slightly modified version of cppformat, by Wildfire Games, for 0 A.D.
+ * Based on cppformat v0.11.0 from https://github.com/cppformat/cppformat
+ */
+
 /*
  Formatting library for C++
 
@@ -39,7 +44,7 @@
 #include <string>
 #include <sstream>
 
-#if _SECURE_SCL
+#if defined(_SECURE_SCL) && _SECURE_SCL
 # include <iterator>
 #endif
 
@@ -78,7 +83,7 @@
 // since version 2013.
 # define FMT_USE_VARIADIC_TEMPLATES \
    (FMT_HAS_FEATURE(cxx_variadic_templates) || \
-       (FMT_GCC_VERSION >= 404 && __cplusplus >= 201103) || _MSC_VER >= 1800)
+       (FMT_GCC_VERSION >= 404 && __cplusplus >= 201103) || (defined(_MSC_VER) && _MSC_VER >= 1800))
 #endif
 
 #ifndef FMT_USE_RVALUE_REFERENCES
@@ -89,7 +94,7 @@
 # else
 #  define FMT_USE_RVALUE_REFERENCES \
     (FMT_HAS_FEATURE(cxx_rvalue_references) || \
-        (FMT_GCC_VERSION >= 403 && __cplusplus >= 201103) || _MSC_VER >= 1600)
+        (FMT_GCC_VERSION >= 403 && __cplusplus >= 201103) || (defined(_MSC_VER) && _MSC_VER >= 1600))
 # endif
 #endif
 
@@ -98,7 +103,7 @@
 #endif
 
 // Define FMT_USE_NOEXCEPT to make C++ Format use noexcept (C++11 feature).
-#if FMT_USE_NOEXCEPT || FMT_HAS_FEATURE(cxx_noexcept) || \
+#if (defined(FMT_USE_NOEXCEPT) && FMT_USE_NOEXCEPT) || FMT_HAS_FEATURE(cxx_noexcept) || \
   (FMT_GCC_VERSION >= 408 && __cplusplus >= 201103)
 # define FMT_NOEXCEPT(expr) noexcept(expr)
 #else
@@ -225,7 +230,7 @@ namespace internal {
 // output buffer, itself to avoid dynamic memory allocation.
 enum { INLINE_BUFFER_SIZE = 500 };
 
-#if _SECURE_SCL
+#if defined(_SECURE_SCL) && _SECURE_SCL
 // Use checked iterator to avoid warnings on MSVC.
 template <typename T>
 inline stdext::checked_array_iterator<T*> make_ptr(T *ptr, std::size_t size) {
@@ -344,7 +349,7 @@ void Array<T, SIZE>::append(const T *begin, const T *end) {
 template <typename Char>
 class BasicCharTraits {
  public:
-#if _SECURE_SCL
+#if defined(_SECURE_SCL) && _SECURE_SCL
   typedef stdext::checked_array_iterator<Char*> CharPtr;
 #else
   typedef Char *CharPtr;
@@ -1306,7 +1311,7 @@ class BasicWriter {
 
   typedef typename internal::CharTraits<Char>::CharPtr CharPtr;
 
-#if _SECURE_SCL
+#if defined(_SECURE_SCL) && _SECURE_SCL
   // Returns pointer value.
   static Char *get(CharPtr p) { return p.base(); }
 #else