diff --git a/toml/datetime.hpp b/toml/datetime.hpp
index d8127c1..36db1e1 100644
--- a/toml/datetime.hpp
+++ b/toml/datetime.hpp
@@ -21,22 +21,7 @@ namespace toml
 namespace detail
 {
 // TODO: find more sophisticated way to handle this
-#if (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 1) || defined(_XOPEN_SOURCE) || defined(_BSD_SOURCE) || defined(_SVID_SOURCE) || defined(_POSIX_SOURCE)
-inline std::tm localtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::localtime_r(src, &dst);
-    if (!result) { throw std::runtime_error("localtime_r failed."); }
-    return dst;
-}
-inline std::tm gmtime_s(const std::time_t* src)
-{
-    std::tm dst;
-    const auto result = ::gmtime_r(src, &dst);
-    if (!result) { throw std::runtime_error("gmtime_r failed."); }
-    return dst;
-}
-#elif defined(_MSC_VER)
+#if defined(_MSC_VER)
 inline std::tm localtime_s(const std::time_t* src)
 {
     std::tm dst;
@@ -51,6 +36,21 @@ inline std::tm gmtime_s(const std::time_t* src)
     if (result) { throw std::runtime_error("gmtime_s failed."); }
     return dst;
 }
+#elif (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 1) || defined(_XOPEN_SOURCE) || defined(_BSD_SOURCE) || defined(_SVID_SOURCE) || defined(_POSIX_SOURCE)
+inline std::tm localtime_s(const std::time_t* src)
+{
+    std::tm dst;
+    const auto result = ::localtime_r(src, &dst);
+    if (!result) { throw std::runtime_error("localtime_r failed."); }
+    return dst;
+}
+inline std::tm gmtime_s(const std::time_t* src)
+{
+    std::tm dst;
+    const auto result = ::gmtime_r(src, &dst);
+    if (!result) { throw std::runtime_error("gmtime_r failed."); }
+    return dst;
+}
 #else // fallback. not threadsafe
 inline std::tm localtime_s(const std::time_t* src)
 {