Index: include/regex
===================================================================
--- include/regex
+++ include/regex
@@ -1192,7 +1192,8 @@
 
 // lookup_classname
 
-ctype_base::mask _LIBCPP_FUNC_VIS __get_classname(const char* __s, bool __icase);
+regex_traits<char>::char_class_type _LIBCPP_FUNC_VIS
+__get_classname(const char* __s, bool __icase);
 
 template <class _CharT>
 template <class _ForwardIterator>
@@ -2184,8 +2185,8 @@
     vector<pair<string_type, string_type> > __ranges_;
     vector<pair<_CharT, _CharT> > __digraphs_;
     vector<string_type> __equivalences_;
-    ctype_base::mask __mask_;
-    ctype_base::mask __neg_mask_;
+    typename regex_traits<_CharT>::char_class_type __mask_;
+    typename regex_traits<_CharT>::char_class_type __neg_mask_;
     bool __negate_;
     bool __icase_;
     bool __collate_;
@@ -2281,10 +2282,10 @@
     void __add_equivalence(const string_type& __s)
         {__equivalences_.push_back(__s);}
     _LIBCPP_INLINE_VISIBILITY
-    void __add_class(ctype_base::mask __mask)
+    void __add_class(typename regex_traits<_CharT>::char_class_type __mask)
         {__mask_ |= __mask;}
     _LIBCPP_INLINE_VISIBILITY
-    void __add_neg_class(ctype_base::mask __mask)
+    void __add_neg_class(typename regex_traits<_CharT>::char_class_type __mask)
         {__neg_mask_ |= __mask;}
 };
 
Index: src/regex.cpp
===================================================================
--- src/regex.cpp
+++ src/regex.cpp
@@ -207,7 +207,7 @@
 struct classnames
 {
     const char* elem_;
-    ctype_base::mask mask_;
+    regex_traits<char>::char_class_type mask_;
 };
 
 #if defined(__clang__)
@@ -254,12 +254,12 @@
     return r;
 }
 
-ctype_base::mask
+regex_traits<char>::char_class_type
 __get_classname(const char* s, bool __icase)
 {
     const classnames* i =
             _VSTD::lower_bound(begin(ClassNames), end(ClassNames), s, use_strcmp());
-    ctype_base::mask r = 0;
+    regex_traits<char>::char_class_type r = 0;
     if (i != end(ClassNames) && strcmp(s, i->elem_) == 0)
     {
         r = i->mask_;
Index: test/re/re.traits/lookup_classname.pass.cpp
===================================================================
--- test/re/re.traits/lookup_classname.pass.cpp
+++ test/re/re.traits/lookup_classname.pass.cpp
@@ -22,7 +22,9 @@
 
 template <class char_type>
 void
-test(const char_type* A, std::ctype_base::mask expected, bool icase = false)
+test(const char_type* A,
+     typename std::regex_traits<char_type>::char_class_type expected,
+     bool icase = false)
 {
     std::regex_traits<char_type> t;
     typedef forward_iterator<const char_type*> F;