diff --git a/test/format-test.cc b/test/format-test.cc
index ac908b8c..4f6fc5fe 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -87,6 +87,11 @@ void std_format(long double value, std::string &result) {
   safe_sprintf(buffer, "%Lg", value);
   result = buffer;
 }
+void std_format(long double value, std::wstring &result) {
+  wchar_t buffer[100];
+  swprintf(buffer, L"%Lg", value);
+  result = buffer;
+}
 #endif
 
 // Checks if writing value to BasicWriter<Char> produces the same result
@@ -284,7 +289,13 @@ TEST(WriterTest, WriteDouble) {
 
 TEST(WriterTest, WriteLongDouble) {
   CHECK_WRITE(4.2l);
-  CHECK_WRITE(-4.2l);
+  CHECK_WRITE_CHAR(-4.2l);
+  std::wstring str;
+  std_format(4.2l, str);
+  if (str[0] != '-')
+    CHECK_WRITE_WCHAR(-4.2l);
+  else
+    fmt::print("warning: long double formatting with std::swprintf is broken");
   CHECK_WRITE(std::numeric_limits<long double>::min());
   CHECK_WRITE(std::numeric_limits<long double>::max());
 }