diff --git a/libcxx/include/__locale_dir/locale_base_api.h b/libcxx/include/__locale_dir/locale_base_api.h
index 9957429c1e7c2..cda6033b03db7 100644
--- a/libcxx/include/__locale_dir/locale_base_api.h
+++ b/libcxx/include/__locale_dir/locale_base_api.h
@@ -56,6 +56,7 @@
 //  int     __strcoll(const char*, const char*, __locale_t);
 //  size_t  __strxfrm(char*, const char*, size_t, __locale_t);
 //
+//  int     __iswctype(wint_t, wctype_t, __locale_t);
 //  int     __iswspace(wint_t, __locale_t);
 //  int     __iswprint(wint_t, __locale_t);
 //  int     __iswcntrl(wint_t, __locale_t);
@@ -192,6 +193,9 @@ inline _LIBCPP_HIDE_FROM_ABI int __wcscoll(const wchar_t* __s1, const wchar_t* _
 inline _LIBCPP_HIDE_FROM_ABI size_t __wcsxfrm(wchar_t* __dest, const wchar_t* __src, size_t __n, __locale_t __loc) {
   return wcsxfrm_l(__dest, __src, __n, __loc);
 }
+inline _LIBCPP_HIDE_FROM_ABI int __iswctype(wint_t __ch, wctype_t __type, __locale_t __loc) {
+  return iswctype_l(__ch, __type, __loc);
+}
 inline _LIBCPP_HIDE_FROM_ABI int __iswspace(wint_t __ch, __locale_t __loc) { return iswspace_l(__ch, __loc); }
 inline _LIBCPP_HIDE_FROM_ABI int __iswprint(wint_t __ch, __locale_t __loc) { return iswprint_l(__ch, __loc); }
 inline _LIBCPP_HIDE_FROM_ABI int __iswcntrl(wint_t __ch, __locale_t __loc) { return iswcntrl_l(__ch, __loc); }
diff --git a/libcxx/include/__locale_dir/support/bsd_like.h b/libcxx/include/__locale_dir/support/bsd_like.h
index da31aeaf3c58e..b3933c71c6b26 100644
--- a/libcxx/include/__locale_dir/support/bsd_like.h
+++ b/libcxx/include/__locale_dir/support/bsd_like.h
@@ -94,6 +94,10 @@ inline _LIBCPP_HIDE_FROM_ABI size_t __strxfrm(char* __dest, const char* __src, s
 }
 
 #if _LIBCPP_HAS_WIDE_CHARACTERS
+inline _LIBCPP_HIDE_FROM_ABI int __iswctype(wint_t __c, wctype_t __type, __locale_t __loc) {
+  return ::iswctype_l(__c, __type, __loc);
+}
+
 inline _LIBCPP_HIDE_FROM_ABI int __iswspace(wint_t __c, __locale_t __loc) { return ::iswspace_l(__c, __loc); }
 
 inline _LIBCPP_HIDE_FROM_ABI int __iswprint(wint_t __c, __locale_t __loc) { return ::iswprint_l(__c, __loc); }
diff --git a/libcxx/include/__locale_dir/support/windows.h b/libcxx/include/__locale_dir/support/windows.h
index 03d05a410fdc3..eca0e17d94c85 100644
--- a/libcxx/include/__locale_dir/support/windows.h
+++ b/libcxx/include/__locale_dir/support/windows.h
@@ -206,6 +206,9 @@ inline _LIBCPP_HIDE_FROM_ABI size_t __strxfrm(char* __dest, const char* __src, s
 }
 
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+inline _LIBCPP_HIDE_FROM_ABI int __iswctype(wint_t __c, wctype_t __type, __locale_t __loc) {
+  return ::_iswctype_l(__c, __type, __loc);
+}
 inline _LIBCPP_HIDE_FROM_ABI int __iswspace(wint_t __c, __locale_t __loc) { return ::_iswspace_l(__c, __loc); }
 inline _LIBCPP_HIDE_FROM_ABI int __iswprint(wint_t __c, __locale_t __loc) { return ::_iswprint_l(__c, __loc); }
 inline _LIBCPP_HIDE_FROM_ABI int __iswcntrl(wint_t __c, __locale_t __loc) { return ::_iswcntrl_l(__c, __loc); }
diff --git a/libcxx/src/locale.cpp b/libcxx/src/locale.cpp
index a1e10401f0b29..599c61ca7a36d 100644
--- a/libcxx/src/locale.cpp
+++ b/libcxx/src/locale.cpp
@@ -1109,11 +1109,11 @@ ctype_byname<wchar_t>::ctype_byname(const string& name, size_t refs)
 ctype_byname<wchar_t>::~ctype_byname() { __locale::__freelocale(__l_); }
 
 bool ctype_byname<wchar_t>::do_is(mask m, char_type c) const {
+  wint_t ch = static_cast<wint_t>(c);
 #  ifdef _LIBCPP_WCTYPE_IS_MASK
-  return static_cast<bool>(iswctype_l(c, m, __l_));
+  return static_cast<bool>(__locale::__iswctype(ch, m, __l_));
 #  else
   bool result = false;
-  wint_t ch   = static_cast<wint_t>(c);
   if ((m & space) == space)
     result |= (__locale::__iswspace(ch, __l_) != 0);
   if ((m & print) == print)
@@ -1179,7 +1179,7 @@ const wchar_t* ctype_byname<wchar_t>::do_is(const char_type* low, const char_typ
 const wchar_t* ctype_byname<wchar_t>::do_scan_is(mask m, const char_type* low, const char_type* high) const {
   for (; low != high; ++low) {
 #  ifdef _LIBCPP_WCTYPE_IS_MASK
-    if (iswctype_l(*low, m, __l_))
+    if (__locale::__iswctype(static_cast<wint_t>(*low), m, __l_))
       break;
 #  else
     wint_t ch = static_cast<wint_t>(*low);
@@ -1210,11 +1210,11 @@ const wchar_t* ctype_byname<wchar_t>::do_scan_is(mask m, const char_type* low, c
 
 const wchar_t* ctype_byname<wchar_t>::do_scan_not(mask m, const char_type* low, const char_type* high) const {
   for (; low != high; ++low) {
+    wint_t ch = static_cast<wint_t>(*low);
 #  ifdef _LIBCPP_WCTYPE_IS_MASK
-    if (!iswctype_l(*low, m, __l_))
+    if (!__locale::__iswctype(ch, m, __l_))
       break;
 #  else
-    wint_t ch = static_cast<wint_t>(*low);
     if ((m & space) == space && __locale::__iswspace(ch, __l_))
       continue;
     if ((m & print) == print && __locale::__iswprint(ch, __l_))