diff --git a/include/list b/include/list
index cbc165b..2e80b2f 100644
--- a/include/list
+++ b/include/list
@@ -129,11 +129,11 @@
     void splice(const_iterator position, list&& x, const_iterator first,
                                                   const_iterator last);
 
-    size_type remove(const value_type& value);
-    template <class Pred> size_type remove_if(Pred pred);
-    size_type unique();
+    size_type remove(const value_type& value); // void before C++20
+    template <class Pred> size_type remove_if(Pred pred); // void before C++20
+    size_type unique();  // void before C++20
     template <class BinaryPredicate>
-        size_type unique(BinaryPredicate binary_pred);
+        size_type unique(BinaryPredicate binary_pred); // void before C++20
     void merge(list& x);
     void merge(list&& x);
     template <class Compare>
@@ -857,6 +857,11 @@
     typedef typename base::const_iterator            const_iterator;
     typedef _VSTD::reverse_iterator<iterator>         reverse_iterator;
     typedef _VSTD::reverse_iterator<const_iterator>   const_reverse_iterator;
+#if _LIBCPP_STD_VER > 17
+	typedef size_type                                __remove_return_type;
+#else
+	typedef void                                     __remove_return_type;
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     list()
@@ -1070,12 +1075,12 @@
     void splice(const_iterator __p, list& __c, const_iterator __i);
     void splice(const_iterator __p, list& __c, const_iterator __f, const_iterator __l);
 
-    size_type remove(const value_type& __x);
-    template <class _Pred> size_type remove_if(_Pred __pred);
+    __remove_return_type remove(const value_type& __x);
+    template <class _Pred> __remove_return_type remove_if(_Pred __pred);
     _LIBCPP_INLINE_VISIBILITY
-    size_type unique() { return unique(__equal_to<value_type>()); }
+    __remove_return_type unique() { return unique(__equal_to<value_type>()); }
     template <class _BinaryPred>
-        size_type unique(_BinaryPred __binary_pred);
+        __remove_return_type unique(_BinaryPred __binary_pred);
     _LIBCPP_INLINE_VISIBILITY
     void merge(list& __c);
 #ifndef _LIBCPP_CXX03_LANG
@@ -2141,7 +2146,7 @@
 }
 
 template <class _Tp, class _Alloc>
-typename list<_Tp, _Alloc>::size_type
+typename list<_Tp, _Alloc>::__remove_return_type
 list<_Tp, _Alloc>::remove(const value_type& __x)
 {
     list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
@@ -2161,12 +2166,12 @@
             ++__i;
     }
 
-    return __deleted_nodes.size();
+    return (__remove_return_type) __deleted_nodes.size();
 }
 
 template <class _Tp, class _Alloc>
 template <class _Pred>
-typename list<_Tp, _Alloc>::size_type
+typename list<_Tp, _Alloc>::__remove_return_type
 list<_Tp, _Alloc>::remove_if(_Pred __pred)
 {
     list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
@@ -2186,12 +2191,12 @@
             ++__i;
     }
 
-    return __deleted_nodes.size();
+    return (__remove_return_type) __deleted_nodes.size();
 }
 
 template <class _Tp, class _Alloc>
 template <class _BinaryPred>
-typename list<_Tp, _Alloc>::size_type
+typename list<_Tp, _Alloc>::__remove_return_type
 list<_Tp, _Alloc>::unique(_BinaryPred __binary_pred)
 {
     list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
@@ -2206,7 +2211,7 @@
             }
     }
     
-    return __deleted_nodes.size();
+    return (__remove_return_type) __deleted_nodes.size();
 }
 
 template <class _Tp, class _Alloc>
diff --git a/test/std/containers/sequences/list/list.ops/remove.pass.cpp b/test/std/containers/sequences/list/list.ops/remove.pass.cpp
index 19a8817..8c9a062 100644
--- a/test/std/containers/sequences/list/list.ops/remove.pass.cpp
+++ b/test/std/containers/sequences/list/list.ops/remove.pass.cpp
@@ -8,7 +8,8 @@
 
 // <list>
 
-// void remove(const value_type& value);
+// void      remove(const value_type& value); // pre-c++20
+// size_type remove(const value_type& value); // c++20 and later
 
 #include <list>
 #include <cassert>
@@ -36,8 +37,16 @@
   {
     int a1[] = {1, 2, 3, 4};
     int a2[] = {1, 2, 4};
-    std::list<int> c(a1, a1 + 4);
+    typedef std::list<int> L;
+    L c(a1, a1 + 4);
+#if TEST_STD_VER > 17
     assert(c.remove(3) == 1);
+	ASSERT_SAME_TYPE(L::size_type, decltype(c.remove(3)));
+#else
+	ASSERT_SAME_TYPE(void,         decltype(c.remove(3)));
+    c.remove(3);
+#endif
+
     assert(c == std::list<int>(a2, a2 + 3));
   }
   { // LWG issue #526
@@ -53,7 +62,11 @@
     std::list<S> c;
     for (int *ip = a1; ip < a1 + 8; ++ip)
       c.push_back(S(*ip));
+#if TEST_STD_VER > 17
     assert(c.remove(c.front()) == 3);
+#else
+    c.remove(c.front());
+#endif
     std::list<S>::const_iterator it = c.begin();
     for (int *ip = a2; ip < a2 + 5; ++ip, ++it) {
       assert(it != c.end());
@@ -67,7 +80,11 @@
     int a1[] = {1, 2, 3, 4};
     int a2[] = {1, 2, 4};
     List c(a1, a1 + 4, Alloc::create());
-      assert(c.remove(3) == 1);
+#if TEST_STD_VER > 17
+    assert(c.remove(3) == 1);
+#else
+    c.remove(3);
+#endif
     assert(c == List(a2, a2 + 3, Alloc::create()));
   }
 #if TEST_STD_VER >= 11
@@ -75,7 +92,11 @@
     int a1[] = {1, 2, 3, 4};
     int a2[] = {1, 2, 4};
     std::list<int, min_allocator<int>> c(a1, a1 + 4);
+#if TEST_STD_VER > 17
     assert(c.remove(3) == 1);
+#else
+    c.remove(3);
+#endif
     assert((c == std::list<int, min_allocator<int>>(a2, a2 + 3)));
   }
 #endif
diff --git a/test/std/containers/sequences/list/list.ops/remove_if.pass.cpp b/test/std/containers/sequences/list/list.ops/remove_if.pass.cpp
index d78f7db..0944e68 100644
--- a/test/std/containers/sequences/list/list.ops/remove_if.pass.cpp
+++ b/test/std/containers/sequences/list/list.ops/remove_if.pass.cpp
@@ -8,7 +8,8 @@
 
 // <list>
 
-// template <class Pred> void remove_if(Pred pred);
+// template <class Pred> void      remove_if(Pred pred); // before C++20
+// template <class Pred> size_type remove_if(Pred pred); // c++20 and later
 
 #include <list>
 #include <cassert>
@@ -28,10 +29,10 @@
     return i < 3;
 }
 
-struct PredLWG529 {
-    PredLWG529 (int i) : i_(i) {};
-    ~PredLWG529() { i_ = -32767; }
-    bool operator() (const PredLWG529 &p) const { return p.i_ == i_; }
+struct PredLWG526 {
+    PredLWG526 (int i) : i_(i) {};
+    ~PredLWG526() { i_ = -32767; }
+    bool operator() (const PredLWG526 &p) const { return p.i_ == i_; }
 
     bool operator==(int i) const { return i == i_;}
     int i_;
@@ -44,9 +45,16 @@
     {
     int a1[] = {1, 2, 3, 4};
     int a2[] = {3, 4};
-    std::list<int> c(a1, a1+4);
+    typedef std::list<int> L;
+    L c(a1, a1+4);
     Predicate cp(g);
+#if TEST_STD_VER > 17
+	ASSERT_SAME_TYPE(L::size_type, decltype(c.remove_if(std::ref(cp))));
     assert(c.remove_if(std::ref(cp)) == 2);
+#else
+	ASSERT_SAME_TYPE(void, decltype(c.remove_if(std::ref(cp))));
+    c.remove_if(std::ref(cp));
+#endif
     assert(c == std::list<int>(a2, a2+2));
     assert(cp.count() == 4);
     }
@@ -55,14 +63,18 @@
     int a2[] = {1, 3};
     std::list<int> c(a1, a1+4);
     Predicate cp(even);
+#if TEST_STD_VER > 17
     assert(c.remove_if(std::ref(cp)) == 2);
+#else
+    c.remove_if(std::ref(cp));
+#endif
     assert(c == std::list<int>(a2, a2+2));
     assert(cp.count() == 4);
     }
     { // LWG issue #526
     int a1[] = {1, 2, 1, 3, 5, 8, 11};
     int a2[] = {2, 3, 5, 8, 11};
-    std::list<PredLWG529> c(a1, a1 + 7);
+    std::list<PredLWG526> c(a1, a1 + 7);
     c.remove_if(std::ref(c.front()));
     assert(c.size() == 5);
     for (size_t i = 0; i < c.size(); ++i)
@@ -78,7 +90,11 @@
     int a2[] = {3, 4};
     std::list<int, min_allocator<int>> c(a1, a1+4);
     Predicate cp(g);
+#if TEST_STD_VER > 17
     assert(c.remove_if(std::ref(cp)) == 2);
+#else
+    c.remove_if(std::ref(cp));
+#endif
     assert((c == std::list<int, min_allocator<int>>(a2, a2+2)));
     assert(cp.count() == 4);
     }
diff --git a/test/std/containers/sequences/list/list.ops/unique.pass.cpp b/test/std/containers/sequences/list/list.ops/unique.pass.cpp
index dc80d03..85c4ec5 100644
--- a/test/std/containers/sequences/list/list.ops/unique.pass.cpp
+++ b/test/std/containers/sequences/list/list.ops/unique.pass.cpp
@@ -8,7 +8,8 @@
 
 // <list>
 
-// void unique();
+// void      unique(); // before C++20
+// size_type unique(); // C++20 and later
 
 #include <list>
 #include <cassert>
@@ -21,8 +22,15 @@
     {
     int a1[] = {2, 1, 1, 4, 4, 4, 4, 3, 3};
     int a2[] = {2, 1, 4, 3};
-    std::list<int> c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+    typedef std::list<int> L;
+    L c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+#if TEST_STD_VER > 17
+	ASSERT_SAME_TYPE(L::size_type, decltype(c.unique()));
     assert(c.unique() == 5);
+#else
+	ASSERT_SAME_TYPE(void,         decltype(c.unique()));
+    c.unique();
+#endif
     assert(c == std::list<int>(a2, a2+4));
     }
 #if TEST_STD_VER >= 11
@@ -30,7 +38,11 @@
     int a1[] = {2, 1, 1, 4, 4, 4, 4, 3, 3};
     int a2[] = {2, 1, 4, 3};
     std::list<int, min_allocator<int>> c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+#if TEST_STD_VER > 17
     assert(c.unique() == 5);
+#else
+    c.unique();
+#endif
     assert((c == std::list<int, min_allocator<int>>(a2, a2+4)));
     }
 #endif
diff --git a/test/std/containers/sequences/list/list.ops/unique_pred.pass.cpp b/test/std/containers/sequences/list/list.ops/unique_pred.pass.cpp
index 6338324..75f8c7b 100644
--- a/test/std/containers/sequences/list/list.ops/unique_pred.pass.cpp
+++ b/test/std/containers/sequences/list/list.ops/unique_pred.pass.cpp
@@ -8,7 +8,8 @@
 
 // <list>
 
-// template <class BinaryPred> void unique(BinaryPred pred);
+// template <class BinaryPred> void      unique(BinaryPred pred); // before C++20
+// template <class BinaryPred> size_type unique(BinaryPred pred); // C++20 and later
 
 #include <list>
 #include <cassert>
@@ -21,10 +22,10 @@
     return x == y;
 }
 
-struct PredLWG529 {
-    PredLWG529 (int i) : i_(i) {};
-    ~PredLWG529() { i_ = -32767; }
-    bool operator() (const PredLWG529 &lhs, const PredLWG529 &rhs) const { return lhs.i_ == rhs.i_; }
+struct PredLWG526 {
+    PredLWG526 (int i) : i_(i) {};
+    ~PredLWG526() { i_ = -32767; }
+    bool operator() (const PredLWG526 &lhs, const PredLWG526 &rhs) const { return lhs.i_ == rhs.i_; }
 
     bool operator==(int i) const { return i == i_;}
     int i_;
@@ -35,16 +36,27 @@
     {
     int a1[] = {2, 1, 1, 4, 4, 4, 4, 3, 3};
     int a2[] = {2, 1, 4, 3};
-    std::list<int> c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+    typedef std::list<int> L;
+    L c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+#if TEST_STD_VER > 17
+	ASSERT_SAME_TYPE(L::size_type, decltype(c.unique(g)));
+    assert(c.unique(g) == 5);
+#else
+	ASSERT_SAME_TYPE(void,         decltype(c.unique(g)));
     c.unique(g);
+#endif
     assert(c == std::list<int>(a2, a2+4));
     }
 
     { // LWG issue #526
     int a1[] = {1, 1, 1, 2, 3, 5, 5, 2, 11};
     int a2[] = {1,       2, 3, 5,    2, 11};
-    std::list<PredLWG529> c(a1, a1 + 9);
+    std::list<PredLWG526> c(a1, a1 + 9);
+#if TEST_STD_VER > 17
+    assert(c.unique(std::ref(c.front())) == 3);
+#else
     c.unique(std::ref(c.front()));
+#endif
     assert(c.size() == 6);
     for (size_t i = 0; i < c.size(); ++i)
     {
@@ -58,7 +70,11 @@
     int a1[] = {2, 1, 1, 4, 4, 4, 4, 3, 3};
     int a2[] = {2, 1, 4, 3};
     std::list<int, min_allocator<int>> c(a1, a1+sizeof(a1)/sizeof(a1[0]));
+#if TEST_STD_VER > 17
+    assert(c.unique(g) == 5);
+#else
     c.unique(g);
+#endif
     assert((c == std::list<int, min_allocator<int>>(a2, a2+4)));
     }
 #endif