Index: libcxx/include/string_view
===================================================================
--- libcxx/include/string_view
+++ libcxx/include/string_view
@@ -225,6 +225,9 @@
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     basic_string_view& operator=(const basic_string_view&) _NOEXCEPT = default;

+    _LIBCPP_CONSTEXPR
+    basic_string_view(nullptr_t, size_t) = delete;
+
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
     basic_string_view(const _CharT* __s, size_type __len) _NOEXCEPT
         : __data(__s), __size(__len)
@@ -234,6 +237,9 @@
 #endif
     }

+    _LIBCPP_CONSTEXPR
+    basic_string_view(nullptr_t) = delete;
+
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
     basic_string_view(const _CharT* __s)
         : __data(__s), __size(std::__char_traits_length_checked<_Traits>(__s)) {}