diff --git a/stl/inc/__msvc_formatter.hpp b/stl/inc/__msvc_formatter.hpp
index d1355eb20fc..8fa4c3017e4 100644
--- a/stl/inc/__msvc_formatter.hpp
+++ b/stl/inc/__msvc_formatter.hpp
@@ -401,11 +401,12 @@ constexpr bool enable_nonlocking_formatter_optimization<basic_string_view<_CharT
 
 template <class _Ty1, class _Ty2>
 constexpr bool enable_nonlocking_formatter_optimization<pair<_Ty1, _Ty2>> =
-    enable_nonlocking_formatter_optimization<_Ty1> && enable_nonlocking_formatter_optimization<_Ty2>;
+    enable_nonlocking_formatter_optimization<remove_cvref_t<_Ty1>>
+    && enable_nonlocking_formatter_optimization<remove_cvref_t<_Ty2>>;
 
 template <class... _Ts>
 constexpr bool enable_nonlocking_formatter_optimization<tuple<_Ts...>> =
-    (enable_nonlocking_formatter_optimization<_Ts> && ...);
+    (enable_nonlocking_formatter_optimization<remove_cvref_t<_Ts>> && ...);
 
 template <class _CharT>
 struct _Fill_align_and_width_specs {
diff --git a/tests/std/tests/P3107R5_enabled_specializations/test.compile.pass.cpp b/tests/std/tests/P3107R5_enabled_specializations/test.compile.pass.cpp
index 53c28d0c0e2..2eed1af8c39 100644
--- a/tests/std/tests/P3107R5_enabled_specializations/test.compile.pass.cpp
+++ b/tests/std/tests/P3107R5_enabled_specializations/test.compile.pass.cpp
@@ -121,12 +121,29 @@ static_assert(enable_nonlocking_formatter_optimization<long double>);
 static_assert(enable_nonlocking_formatter_optimization<nullptr_t>);
 static_assert(enable_nonlocking_formatter_optimization<void*>);
 static_assert(enable_nonlocking_formatter_optimization<const void*>);
-static_assert(enable_nonlocking_formatter_optimization<pair<int, int>>);
-static_assert(!enable_nonlocking_formatter_optimization<pair<unoptimized, int>>);
-static_assert(!enable_nonlocking_formatter_optimization<pair<int, unoptimized>>);
-static_assert(enable_nonlocking_formatter_optimization<tuple<int, int>>);
-static_assert(!enable_nonlocking_formatter_optimization<tuple<unoptimized, int>>);
-static_assert(!enable_nonlocking_formatter_optimization<tuple<int, unoptimized>>);
+
+// Extended to test LWG-4399 "enable_nonlocking_formatter_optimization for pair and tuple needs remove_cvref_t"
+template <template <class, class> class PairOrTuple, class T, class U, bool Expected>
+constexpr void test_lwg_4399_impl() {
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<T, U>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<T&, U>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<T, U&>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<const T, U>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<T, const U>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<const T&, U>> == Expected);
+    static_assert(enable_nonlocking_formatter_optimization<PairOrTuple<T, const U&>> == Expected);
+}
+
+template <class T, class U, bool Expected>
+constexpr bool test_lwg_4399() {
+    test_lwg_4399_impl<pair, T, U, Expected>();
+    test_lwg_4399_impl<tuple, T, U, Expected>();
+    return true;
+}
+
+static_assert(test_lwg_4399<int, int, true>());
+static_assert(test_lwg_4399<unoptimized, int, false>());
+static_assert(test_lwg_4399<int, unoptimized, false>());
 
 // Validate that various ranges are unoptimized
 static_assert(!enable_nonlocking_formatter_optimization<list<int>>);