diff --git a/test/gtest-extra-test.cc b/test/gtest-extra-test.cc
index 077bd476..9215fa7c 100644
--- a/test/gtest-extra-test.cc
+++ b/test/gtest-extra-test.cc
@@ -504,28 +504,6 @@ TEST(FileTest, Read) {
   EXPECT_READ(f, "language: cpp");
 }
 
-#ifdef _WIN32
-// The count argument to the read function is unsigned on Windows, so check
-// if integer overflow is handled properly.
-TEST(FileTest, ReadCountOverflow) {
-  if (sizeof(std::size_t) == sizeof(unsigned))
-    return;
-  File read_end, write_end;
-  File::pipe(read_end, write_end);
-  Write(write_end, "test");
-  write_end.close();
-  char buffer[4];
-  std::size_t offset = 0;
-  std::size_t count = std::numeric_limits<unsigned>::max() + std::size_t(1);
-  std::streamsize n = 0;
-  do {
-    n = read_end.read(buffer + offset, count);
-    offset += n;
-  } while (n != 0);
-  EXPECT_EQ("test", std::string(buffer, offset));
-}
-#endif
-
 TEST(FileTest, ReadError) {
   File read_end, write_end;
   File::pipe(read_end, write_end);
diff --git a/test/gtest-extra.cc b/test/gtest-extra.cc
index 5766cb14..ec08f87a 100644
--- a/test/gtest-extra.cc
+++ b/test/gtest-extra.cc
@@ -30,6 +30,7 @@
 #if FMT_USE_FILE_DESCRIPTORS
 
 #include <errno.h>
+#include <limits.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ -51,6 +52,19 @@
     result = (expression); \
   } while (result == -1 && errno == EINTR)
 
+namespace {
+// TODO: test
+#ifdef _WIN32
+// On Windows the count argument to read and write is unsigned, so convert
+// it from size_t preventing integer overflow.
+inline unsigned ConvertRWCount(std::size_t count) {
+  return count <= UINT_MAX ? count : UINT_MAX;
+}
+#else
+inline std::size_t ConvertRWCount(std::size_t count) { return count; }
+#endif
+}
+
 BufferedFile::~BufferedFile() FMT_NOEXCEPT(true) {
   if (file_ && std::fclose(file_) != 0)
     fmt::ReportSystemError(errno, "cannot close file");
@@ -102,16 +116,6 @@ void File::close() {
     fmt::ThrowSystemError(errno, "cannot close file");
 }
 
-#ifdef _WIN32
-// On Windows the count argument to read and write is unsigned, so convert
-// it from size_t preventing integer overflow.
-inline unsigned ConvertRWCount(std::size_t count) {
-  return count <= UINT_MAX ? count : UINT_MAX;
-}
-#else
-inline std::size_t ConvertRWCount(std::size_t count) { return count; }
-#endif
-
 std::streamsize File::read(void *buffer, std::size_t count) {
   std::streamsize result = 0;
   FMT_RETRY(result, ::FMT_POSIX(read(fd_, buffer, ConvertRWCount(count))));
@@ -122,7 +126,7 @@ std::streamsize File::read(void *buffer, std::size_t count) {
 
 std::streamsize File::write(const void *buffer, std::size_t count) {
   std::streamsize result = 0;
-  FMT_RETRY(result, ::FMT_POSIX(write(fd_, buffer, count)));
+  FMT_RETRY(result, ::FMT_POSIX(write(fd_, buffer, ConvertRWCount(count))));
   if (result == -1)
     fmt::ThrowSystemError(errno, "cannot write to file");
   return result;