diff --git a/libstdc++-v3/include/bits/locale_facets.h b/libstdc++-v3/include/bits/locale_facets.h
index 03724cf..012857f 100644
--- a/libstdc++-v3/include/bits/locale_facets.h
+++ b/libstdc++-v3/include/bits/locale_facets.h
@@ -136,6 +136,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return __s;
     }
 
+  template<typename>
+    struct __is_string
+    {
+	enum _Value { _value = 0 };
+    };
+
+  template<typename _CharT, typename _Traits, typename _Alloc>
+    struct __is_string<basic_string<_CharT, _Traits, _Alloc> >
+    {
+	enum _Value { _value = 1 };
+    };
 
   // 22.2.1.1  Template class ctype
   // Include host and configuration specific ctype enums for ctype_base.
@@ -614,6 +625,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _CharT>
     class ctype : public __ctype_abstract_base<_CharT>
     {
+#if __cplusplus >= 201103L
+      static_assert(!__is_string<_CharT>::_value,
+		    "std::basic_string used as a character type");
+#endif
     public:
       // Types:
       typedef _CharT			char_type;
diff --git a/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc b/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc
new file mode 100644
index 0000000..987fa8e
--- /dev/null
+++ b/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc
@@ -0,0 +1,73 @@
+// { dg-do compile { target c++11 } }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-error "used as a character type" "" { target *-*-* } 0 }
+
+#include <locale>
+
+template <class Char, int I>
+struct trait: std::char_traits<Char> {};
+
+template <class Char, int I>
+auto make_str()
+{
+  return std::basic_string<Char, trait<Char, I>>{};
+}
+
+void test01()
+{
+  const auto& loc = std::locale::classic();
+
+  std::isspace(std::string{}, loc);		// { dg-error "required from here" }
+  std::isprint(make_str<char, 0>(), loc);	// { dg-error "required from here" }
+  std::iscntrl(make_str<char, 1>(), loc);	// { dg-error "required from here" }
+  std::isupper(make_str<char, 2>(), loc);	// { dg-error "required from here" }
+  std::islower(make_str<char, 3>(), loc);	// { dg-error "required from here" }
+  std::isalpha(make_str<char, 4>(), loc);	// { dg-error "required from here" }
+  std::isdigit(make_str<char, 5>(), loc);	// { dg-error "required from here" }
+  std::ispunct(make_str<char, 6>(), loc);	// { dg-error "required from here" }
+  std::isxdigit(make_str<char, 7>(), loc);	// { dg-error "required from here" }
+  std::isalnum(make_str<char, 8>(), loc);	// { dg-error "required from here" }
+  std::isgraph(make_str<char, 9>(), loc);	// { dg-error "required from here" }
+  std::isblank(make_str<char, 10>(), loc);	// { dg-error "required from here" }
+  std::toupper(make_str<char, 11>(), loc);	// { dg-error "required from here" }
+  std::tolower(make_str<char, 12>(), loc);	// { dg-error "required from here" }
+}
+
+#ifdef _GLIBCXX_USE_WCHAR_T
+void test02()
+{
+  const auto& loc = std::locale::classic();
+
+  std::isspace(std::wstring{}, loc);		// { dg-error "required from here" }
+  std::isprint(make_str<wchar_t, 0>(), loc);	// { dg-error "required from here" }
+  std::iscntrl(make_str<wchar_t, 1>(), loc);	// { dg-error "required from here" }
+  std::isupper(make_str<wchar_t, 2>(), loc);	// { dg-error "required from here" }
+  std::islower(make_str<wchar_t, 3>(), loc);	// { dg-error "required from here" }
+  std::isalpha(make_str<wchar_t, 4>(), loc);	// { dg-error "required from here" }
+  std::isdigit(make_str<wchar_t, 5>(), loc);	// { dg-error "required from here" }
+  std::ispunct(make_str<wchar_t, 6>(), loc);	// { dg-error "required from here" }
+  std::isxdigit(make_str<wchar_t, 7>(), loc);	// { dg-error "required from here" }
+  std::isalnum(make_str<wchar_t, 8>(), loc);	// { dg-error "required from here" }
+  std::isgraph(make_str<wchar_t, 9>(), loc);	// { dg-error "required from here" }
+  std::isblank(make_str<wchar_t, 10>(), loc);	// { dg-error "required from here" }
+  std::toupper(make_str<wchar_t, 11>(), loc);	// { dg-error "required from here" }
+  std::tolower(make_str<wchar_t, 12>(), loc);	// { dg-error "required from here" }
+}
+#endif
