Index: test/localization/locales/locale.convenience/conversions/conversions.buffer/ctor.pass.cpp
===================================================================
--- test/localization/locales/locale.convenience/conversions/conversions.buffer/ctor.pass.cpp	(revision 189387)
+++ test/localization/locales/locale.convenience/conversions/conversions.buffer/ctor.pass.cpp	(working copy)
@@ -37,6 +37,10 @@
 int main()
 {
     typedef std::wbuffer_convert<std::codecvt_utf8<wchar_t> > B;
+#if _LIBCPP_STD_VER > 11
+    static_assert(!std::is_convertible<std::streambuf*, B>::value, "");
+    static_assert( std::is_constructible<B, std::streambuf*>::value, "");
+#endif
     {
         B b;
         assert(b.rdbuf() == nullptr);
Index: test/localization/locales/locale.convenience/conversions/conversions.string/ctor_codecvt.pass.cpp
===================================================================
--- test/localization/locales/locale.convenience/conversions/conversions.string/ctor_codecvt.pass.cpp	(revision 189387)
+++ test/localization/locales/locale.convenience/conversions/conversions.string/ctor_codecvt.pass.cpp	(working copy)
@@ -30,5 +30,9 @@
         typedef std::wstring_convert<Codecvt> Myconv;
         Myconv myconv(new Codecvt);
         assert(myconv.converted() == 0);
+#if _LIBCPP_STD_VER > 11
+        static_assert(!std::is_convertible<Codecvt*, Myconv>::value, "");
+        static_assert( std::is_constructible<Myconv, Codecvt*>::value, "");
+#endif
     }
 }
Index: test/localization/locales/locale.convenience/conversions/conversions.string/ctor_err_string.pass.cpp
===================================================================
--- test/localization/locales/locale.convenience/conversions/conversions.string/ctor_err_string.pass.cpp	(revision 189387)
+++ test/localization/locales/locale.convenience/conversions/conversions.string/ctor_err_string.pass.cpp	(working copy)
@@ -22,6 +22,10 @@
 {
     typedef std::codecvt_utf8<wchar_t> Codecvt;
     typedef std::wstring_convert<Codecvt> Myconv;
+#if _LIBCPP_STD_VER > 11
+    static_assert(!std::is_convertible<std::string, Myconv>::value, "");
+    static_assert( std::is_constructible<Myconv, std::string>::value, "");
+#endif
     {
         Myconv myconv;
         try