diff --git a/libcxx/include/__algorithm/sort.h b/libcxx/include/__algorithm/sort.h
index 1b878c33c7a16..6f6d7bd87a593 100644
--- a/libcxx/include/__algorithm/sort.h
+++ b/libcxx/include/__algorithm/sort.h
@@ -28,8 +28,8 @@
 #include <__iterator/iterator_traits.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/disjunction.h>
-#include <__type_traits/is_arithmetic.h>
 #include <__type_traits/is_constant_evaluated.h>
+#include <__type_traits/is_trivially_copyable.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <climits>
@@ -144,7 +144,7 @@ template <class _Compare, class _Iter, class _Tp = typename iterator_traits<_Ite
 using __use_branchless_sort =
     integral_constant<bool,
                       __libcpp_is_contiguous_iterator<_Iter>::value && sizeof(_Tp) <= sizeof(void*) &&
-                          is_arithmetic<_Tp>::value && __is_simple_comparator<_Compare>::value>;
+                          is_trivially_copyable<_Tp>::value && __is_simple_comparator<_Compare>::value>;
 
 namespace __detail {
 
@@ -158,6 +158,8 @@ template <class _Compare, class _RandomAccessIterator>
 inline _LIBCPP_HIDE_FROM_ABI void __cond_swap(_RandomAccessIterator __x, _RandomAccessIterator __y, _Compare __c) {
   // Note: this function behaves correctly even with proxy iterators (because it relies on `value_type`).
   using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
+  static_assert(is_trivially_copyable<value_type>::value,
+                "Copying must have no side effects distinguishable from swapping/moving");
   bool __r         = __c(*__x, *__y);
   value_type __tmp = __r ? *__x : *__y;
   *__y             = __r ? *__y : *__x;
@@ -171,6 +173,8 @@ inline _LIBCPP_HIDE_FROM_ABI void
 __partially_sorted_swap(_RandomAccessIterator __x, _RandomAccessIterator __y, _RandomAccessIterator __z, _Compare __c) {
   // Note: this function behaves correctly even with proxy iterators (because it relies on `value_type`).
   using value_type = typename iterator_traits<_RandomAccessIterator>::value_type;
+  static_assert(is_trivially_copyable<value_type>::value,
+                "Copying must have no side effects distinguishable from swapping/moving");
   bool __r         = __c(*__z, *__x);
   value_type __tmp = __r ? *__z : *__x;
   *__z             = __r ? *__x : *__z;
diff --git a/libcxx/test/libcxx/algorithms/sort_stability.pass.cpp b/libcxx/test/libcxx/algorithms/sort_stability.pass.cpp
index 712f12c255935..8856ca019f721 100644
--- a/libcxx/test/libcxx/algorithms/sort_stability.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/sort_stability.pass.cpp
@@ -68,8 +68,7 @@ void test_same() {
   auto snapshot_custom_v = v;
   std::sort(v.begin(), v.end());
   std::sort(snapshot_v.begin(), snapshot_v.end());
-  std::sort(snapshot_custom_v.begin(), snapshot_custom_v.end(),
-            [](const EqualType&, const EqualType&) { return false; });
+  std::sort(snapshot_custom_v.begin(), snapshot_custom_v.end(), std::less<EqualType>());
   bool all_equal = true;
   for (int i = 0; i < kSize; ++i) {
     if (v[i].value != snapshot_v[i].value || v[i].value != snapshot_custom_v[i].value) {