diff --git a/libstdc++-v3/config/locale/generic/ctype_members.cc b/libstdc++-v3/config/locale/generic/ctype_members.cc
index 607c8bb1b..b197acb1f 100644
--- a/libstdc++-v3/config/locale/generic/ctype_members.cc
+++ b/libstdc++-v3/config/locale/generic/ctype_members.cc
@@ -133,6 +133,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     return __hi;
   }
 
+#ifndef _GLIBCXX_CTYPE_WCHAR_T_DO_IS_DEFINED
   bool
   ctype<wchar_t>::
   do_is(mask __m, char_type __c) const
@@ -186,6 +187,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       ++__lo;
     return __lo;
   }
+#endif //  _GLIBCXX_CTYPE_WCHAR_T_DO_IS_DEFINED
 
   wchar_t
   ctype<wchar_t>::
@@ -205,6 +207,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     return __hi;
   }
 
+#if defined(__WCHAR_MIN__) && __WCHAR_MIN__ == 0
+// Disable wc >= 0 warnings for unsigned wchar_t.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wtype-limits"
+#endif
+
   char
   ctype<wchar_t>::
   do_narrow(wchar_t __wc, char __dfault) const
@@ -244,6 +252,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     return __hi;
   }
 
+#if defined(__WCHAR_MIN__) && __WCHAR_MIN__ == 0
+#pragma GCC diagnostic pop
+#endif
+
   void
   ctype<wchar_t>::_M_initialize_ctype() throw()
   {
diff --git a/libstdc++-v3/config/os/os2/os_defines.h b/libstdc++-v3/config/os/os2/os_defines.h
index 50ea32251..8da850234 100644
--- a/libstdc++-v3/config/os/os2/os_defines.h
+++ b/libstdc++-v3/config/os/os2/os_defines.h
@@ -33,4 +33,7 @@
 // System-specific #define, typedefs, corrections, etc, go here.  This
 // file will come before all others.
 
+// We have ctype::do_is and do_scan* specialised in ctype_inline.h.
+#define _GLIBCXX_CTYPE_WCHAR_T_DO_IS_DEFINED 1
+
 #endif