diff --git a/include/string_view b/include/string_view
index 1a94ac0..07fcf44 100644
--- a/include/string_view
+++ b/include/string_view
@@ -304,6 +304,9 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     basic_string_view& operator=(const basic_string_view&) _NOEXCEPT = default;
 
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    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)
@@ -348,7 +351,7 @@ public:
     basic_string_view(const _CharT* __s)
         : __data_(__s), __size_(_VSTD::__char_traits_length_checked<_Traits>(__s)) {}
 
-#if _LIBCPP_STD_VER >= 23
+#if _LIBCPP_STD_VER >= 20
     basic_string_view(nullptr_t) = delete;
 #endif
 
@@ -734,7 +737,7 @@ public:
     { return ends_with(basic_string_view(__s)); }
 #endif
 
-#if _LIBCPP_STD_VER >= 23
+#if _LIBCPP_STD_VER >= 20
     constexpr _LIBCPP_INLINE_VISIBILITY
     bool contains(basic_string_view __sv) const noexcept
     { return find(__sv) != npos; }