diff --git a/libcxx/benchmarks/map.bench.cpp b/libcxx/benchmarks/map.bench.cpp
--- a/libcxx/benchmarks/map.bench.cpp
+++ b/libcxx/benchmarks/map.bench.cpp
@@ -168,6 +168,29 @@
   std::string name() const { return "BM_ConstructorMove" + baseName(); }
 };
 
+struct CopyAssignment : Base {
+  using Base::Base;
+
+  void run(benchmark::State& State) const {
+    auto Data = makeTestingSets(MapSize, Mode::Hit, Shuffle::None, 1);
+    auto& Map = Data.Maps.front();
+    while (State.KeepRunningBatch(MapSize)) {
+#ifndef VALIDATE
+      std::map<uint64_t, int64_t> M;
+      M = Map;
+      benchmark::DoNotOptimize(M);
+#else
+      std::map<uint64_t, int64_t> M;
+      M = Map;
+      if (M != Map)
+        State.SkipWithError("Map copy assignment not identical");
+#endif
+    }
+  }
+
+  std::string name() const { return "BM_CopyAssignment" + baseName(); }
+};
+
 //*******************************************************************|
 //                           Capacity                                |
 //*******************************************************************|
@@ -1006,6 +1029,7 @@
   makeCartesianProductBenchmark<ConstructorIterator>(MapSize);
   makeCartesianProductBenchmark<ConstructorCopy>(MapSize);
   makeCartesianProductBenchmark<ConstructorMove>(MapSize);
+  makeCartesianProductBenchmark<CopyAssignment>(MapSize);
 
   // Capacity
   makeCartesianProductBenchmark<Empty>(MapSize);
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -1095,7 +1095,6 @@
     explicit __tree(const allocator_type& __a);
     __tree(const value_compare& __comp, const allocator_type& __a);
     __tree(const __tree& __t);
-    __tree& operator=(const __tree& __t);
     template <class _ForwardIterator>
         void __assign_unique(_ForwardIterator __first, _ForwardIterator __last);
     template <class _InputIterator>
@@ -1534,6 +1533,8 @@
 
     template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
     template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS set;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS multiset;
 };
 
 template <class _Tp, class _Compare, class _Allocator>
@@ -1609,19 +1610,6 @@
     return static_cast<__node_pointer>(_VSTD::__tree_leaf(__cache->__left_));
 }
 
-template <class _Tp, class _Compare, class _Allocator>
-__tree<_Tp, _Compare, _Allocator>&
-__tree<_Tp, _Compare, _Allocator>::operator=(const __tree& __t)
-{
-    if (this != _VSTD::addressof(__t))
-    {
-        value_comp() = __t.value_comp();
-        __copy_assign_alloc(__t);
-        __assign_multi(__t.begin(), __t.end());
-    }
-    return *this;
-}
-
 template <class _Tp, class _Compare, class _Allocator>
 template <class _ForwardIterator>
 void
diff --git a/libcxx/include/map b/libcxx/include/map
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -1077,16 +1077,12 @@
     _LIBCPP_INLINE_VISIBILITY
     map& operator=(const map& __m)
         {
-#ifndef _LIBCPP_CXX03_LANG
-            __tree_ = __m.__tree_;
-#else
             if (this != _VSTD::addressof(__m)) {
                 __tree_.clear();
                 __tree_.value_comp() = __m.__tree_.value_comp();
                 __tree_.__copy_assign_alloc(__m.__tree_);
                 insert(__m.begin(), __m.end());
             }
-#endif
             return *this;
         }
 
@@ -1863,16 +1859,12 @@
     _LIBCPP_INLINE_VISIBILITY
     multimap& operator=(const multimap& __m)
         {
-#ifndef _LIBCPP_CXX03_LANG
-            __tree_ = __m.__tree_;
-#else
             if (this != _VSTD::addressof(__m)) {
                 __tree_.clear();
                 __tree_.value_comp() = __m.__tree_.value_comp();
                 __tree_.__copy_assign_alloc(__m.__tree_);
                 insert(__m.begin(), __m.end());
             }
-#endif
             return *this;
         }
 
diff --git a/libcxx/include/set b/libcxx/include/set
--- a/libcxx/include/set
+++ b/libcxx/include/set
@@ -591,7 +591,12 @@
     _LIBCPP_INLINE_VISIBILITY
     set& operator=(const set& __s)
         {
-            __tree_ = __s.__tree_;
+            if (this != _VSTD::addressof(__s)) {
+                __tree_.clear();
+                __tree_.value_comp() = __s.__tree_.value_comp();
+                __tree_.__copy_assign_alloc(__s.__tree_);
+                insert(__s.begin(), __s.end());
+            }
             return *this;
         }
 
@@ -1125,7 +1130,12 @@
     _LIBCPP_INLINE_VISIBILITY
     multiset& operator=(const multiset& __s)
         {
-            __tree_ = __s.__tree_;
+            if (this != _VSTD::addressof(__s)) {
+                __tree_.clear();
+                __tree_.value_comp() = __s.__tree_.value_comp();
+                __tree_.__copy_assign_alloc(__s.__tree_);
+                insert(__s.begin(), __s.end());
+            }
             return *this;
         }