diff --git a/libcxx/include/valarray b/libcxx/include/valarray
--- a/libcxx/include/valarray
+++ b/libcxx/include/valarray
@@ -136,6 +136,7 @@
     void operator>>=(const valarray<value_type>& v) const;
 
     void operator=(const value_type& x) const;
+    void operator=(const valarray<T>& val_arr) const;
 
     slice_array() = delete;
 };
@@ -1264,6 +1265,9 @@
     _LIBCPP_INLINE_VISIBILITY
     void operator=(const value_type& __x) const;
 
+    _LIBCPP_INLINE_VISIBILITY
+    void operator=(const valarray<value_type>& __va) const;
+
 private:
     _LIBCPP_INLINE_VISIBILITY
     slice_array(const slice& __sl, const valarray<value_type>& __v)
@@ -1303,6 +1307,15 @@
         *__t = __v[__i];
 }
 
+template <class _Tp>
+inline void
+slice_array<_Tp>::operator=(const valarray<value_type>& __va) const
+{
+    value_type* __t = __vp_;
+    for (size_t __i = 0; __i < __va.size(); ++__i, __t += __stride_)
+        *__t = __va[__i];
+}
+
 template <class _Tp>
 template <class _Expr>
 inline
diff --git a/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/template.pass.cpp b/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/template.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/template.pass.cpp
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <valarray>
+
+// template <class T> class slice_array
+
+// void operator=(const T& value) const;
+
+#include <valarray>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+    double a[] = { 0, 0, 0 };
+    std::valarray<double> m(a, sizeof(a)/sizeof(a[0]));
+    std::slice_array<double> s = m[std::slice(0, 3, 1)];
+    s = 42;
+    assert(m[0] == 42);
+    assert(m[1] == 42);
+    assert(m[2] == 42);
+
+    ASSERT_SAME_TYPE(decltype(s = 42), void);
+
+    return 0;
+}
diff --git a/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/valarray.pass.cpp b/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/valarray.pass.cpp
--- a/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/valarray.pass.cpp
+++ b/libcxx/test/std/numerics/numarray/template.slice.array/slice.arr.assign/valarray.pass.cpp
@@ -23,7 +23,8 @@
     int a2[] = {-1, -2, -3, -4, -5};
     std::valarray<int> v1(a1, sizeof(a1)/sizeof(a1[0]));
     std::valarray<int> v2(a2, sizeof(a2)/sizeof(a2[0]));
-    v1[std::slice(1, 5, 3)] = v2;
+    std::slice_array<int> s1 = v1[std::slice(1, 5, 3)];
+    s1 = v2;
     assert(v1.size() == 16);
     assert(v1[ 0] ==  0);
     assert(v1[ 1] == -1);
@@ -42,5 +43,19 @@
     assert(v1[14] == 14);
     assert(v1[15] == 15);
 
-  return 0;
+    ASSERT_SAME_TYPE(decltype(s1 = v2), void);
+
+// The initializer list constructor is disabled in C++03 mode.
+#if TEST_STD_VER > 03
+    std::valarray<double> m = { 0, 0, 0 };
+    std::slice_array<double> s2 = m[std::slice(0, 3, 1)];
+    s2 = { 1, 2, 3 };
+    assert(m[0] == 1);
+    assert(m[1] == 2);
+    assert(m[2] == 3);
+
+    ASSERT_SAME_TYPE(decltype(s2 = {1, 2, 3}), void);
+#endif // TEST_STD_VER > 03
+
+    return 0;
 }