diff --git a/stl/inc/xutility b/stl/inc/xutility
index a7c611ce694..7f638ead249 100644
--- a/stl/inc/xutility
+++ b/stl/inc/xutility
@@ -5997,8 +5997,12 @@ _NODISCARD _CONSTEXPR_BIT_CAST bool _Is_inf(const _Ty _Xx) { // constexpr isinf(
 // FUNCTION TEMPLATE _Is_finite
 template <class _Ty, enable_if_t<is_floating_point_v<_Ty>, int> = 0>
 _NODISCARD _CONSTEXPR_BIT_CAST bool _Is_finite(const _Ty _Xx) { // constexpr isfinite()
+#if defined(__LDBL_DIG__) && __LDBL_DIG__ == 18
+    return _CSTD _LDtest(&_Xx) == _FINITE;
+#else // ^^^ 80-bit long double (not supported by MSVC in general, see GH-1316) / 64-bit long double vvv
     using _Traits = _Floating_type_traits<_Ty>;
     return _Float_abs_bits(_Xx) < _Traits::_Shifted_exponent_mask;
+#endif // 64-bit long double
 }
 
 // STRUCT _Nontrivial_dummy_type