diff --git a/CMakeLists.txt b/CMakeLists.txt
index 149b659..c1d1371 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,6 +21,10 @@ include(cmake/deps_occ.cmake)
 # Add an option to enable static builds
 OPTION(BUILD_STATIC "Build STP2GLB as a static executable." OFF)
 
+if (WIN32 AND DEFINED WIN32_WINNT)
+    add_compile_definitions(_WIN32_WINNT=${WIN32_WINNT})
+endif ()
+
 if (BUILD_STATIC)
     message(STATUS "Building STP2GLB as a static executable.")
 
diff --git a/src/third_party/httplib.h b/src/third_party/httplib.h
index db55d07..b3a2c80 100644
--- a/src/third_party/httplib.h
+++ b/src/third_party/httplib.h
@@ -32,9 +32,9 @@
 #endif
 
 #ifdef _WIN32
-#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
+#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0601
 #error                                                                         \
-    "cpp-httplib doesn't support Windows 8 or lower. Please use Windows 10 or later."
+    "cpp-httplib doesn't support platforms older than Windows 7 SP1."
 #endif
 #endif
 
@@ -3083,8 +3083,14 @@ inline bool mmap::open(const char *path) {
   auto wpath = u8string_to_wstring(path);
   if (wpath.empty()) { return false; }
 
-  hFile_ = ::CreateFile2(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ,
-                         OPEN_EXISTING, NULL);
+  hFile_ =
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0602
+      ::CreateFile2(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ,
+                    OPEN_EXISTING, NULL);
+#else
+      ::CreateFileW(wpath.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL,
+                    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+#endif
 
   if (hFile_ == INVALID_HANDLE_VALUE) { return false; }
 
@@ -3101,7 +3107,17 @@ inline bool mmap::open(const char *path) {
   size_ = static_cast<size_t>(size.QuadPart);
 
   hMapping_ =
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0602
       ::CreateFileMappingFromApp(hFile_, NULL, PAGE_READONLY, size_, NULL);
+#else
+      ::CreateFileMappingW(
+          hFile_, NULL, PAGE_READONLY,
+          static_cast<DWORD>((static_cast<unsigned long long>(size_) >> 32) &
+                             0xffffffffULL),
+          static_cast<DWORD>(static_cast<unsigned long long>(size_) &
+                             0xffffffffULL),
+          NULL);
+#endif
 
   // Special treatment for an empty file...
   if (hMapping_ == NULL && size_ == 0) {
@@ -3115,7 +3131,12 @@ inline bool mmap::open(const char *path) {
     return false;
   }
 
-  addr_ = ::MapViewOfFileFromApp(hMapping_, FILE_MAP_READ, 0, 0);
+  addr_ =
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0602
+      ::MapViewOfFileFromApp(hMapping_, FILE_MAP_READ, 0, 0);
+#else
+      ::MapViewOfFile(hMapping_, FILE_MAP_READ, 0, 0, 0);
+#endif
 
   if (addr_ == nullptr) {
     close();