diff --git a/posix.cc b/posix.cc
index f5060616..0efb5aff 100644
--- a/posix.cc
+++ b/posix.cc
@@ -140,13 +140,19 @@ void fmt::File::close() {
 
 fmt::LongLong fmt::File::size() const {
 #ifdef _WIN32
-  LARGE_INTEGER filesize = {};
+  // Use GetFileSize instead of GetFileSizeEx for the case when _WIN32_WINNT
+  // is less than 0x0500 as is the case with some default MinGW builds.
+  // Both functions support large file sizes.
+  DWORD size_upper = 0;
   HANDLE handle = reinterpret_cast<HANDLE>(_get_osfhandle(fd_));
-  if (!FMT_SYSTEM(GetFileSizeEx(handle, &filesize)))
-    throw WindowsError(GetLastError(), "cannot get file size");
-  FMT_STATIC_ASSERT(sizeof(fmt::LongLong) >= sizeof(filesize.QuadPart),
-      "return type of File::size is not large enough");
-  return filesize.QuadPart;
+  DWORD size_lower = FMT_SYSTEM(GetFileSize(handle, &size_upper));
+  if (size_lower == INVALID_FILE_SIZE) {
+    DWORD error = GetLastError();
+    if (error != NO_ERROR)
+      throw WindowsError(GetLastError(), "cannot get file size");
+  }
+  fmt::ULongLong size = size_upper;
+  return (size << sizeof(DWORD) * CHAR_BIT) | size_lower;
 #else
   typedef struct stat Stat;
   Stat file_stat = Stat();
diff --git a/test/posix-test.cc b/test/posix-test.cc
index c9529688..61d95c85 100644
--- a/test/posix-test.cc
+++ b/test/posix-test.cc
@@ -105,15 +105,17 @@ errno_t test::sopen_s(
 
 static LONGLONG max_file_size() { return std::numeric_limits<LONGLONG>::max(); }
 
-BOOL test::GetFileSizeEx(HANDLE hFile, PLARGE_INTEGER lpFileSize) {
+DWORD test::GetFileSize(HANDLE hFile, LPDWORD lpFileSizeHigh) {
   if (fstat_sim == ERROR) {
     SetLastError(ERROR_ACCESS_DENIED);
     return FALSE;
   }
-  BOOL result = ::GetFileSizeEx(hFile, lpFileSize);
-  if (fstat_sim == MAX_SIZE)
-    lpFileSize->QuadPart = max_file_size();
-  return result;
+  if (fstat_sim == MAX_SIZE) {
+    DWORD max = std::numeric_limits<DWORD>::max();
+    *lpFileSizeHig = max >> 1;
+    return max;
+  }
+  return ::GetFileSize(hFile, lpFileSizeHigh);
 }
 #endif
 
diff --git a/test/posix-test.h b/test/posix-test.h
index a43ce1ef..17bf0c97 100644
--- a/test/posix-test.h
+++ b/test/posix-test.h
@@ -51,7 +51,7 @@ typedef unsigned size_t;
 typedef int ssize_t;
 errno_t sopen_s(
     int* pfh, const char *filename, int oflag, int shflag, int pmode);
-BOOL GetFileSizeEx(HANDLE hFile, PLARGE_INTEGER lpFileSize);
+DWORD GetFileSize(HANDLE hFile, LPDWORD lpFileSizeHigh);
 #endif
 
 int close(int fildes);