diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 077372cde2b5..3e606d290e24 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,7 @@
+2011-02-16  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+	* include/bits/regex.h (match_results::format): Use char_traits.
+
 2011-02-16  Benjamin Kosnik  <bkoz@redhat.com>
 
 	* include/std/atomic: Remove atomic_address, uplift to N3225.
diff --git a/libstdc++-v3/include/bits/regex.h b/libstdc++-v3/include/bits/regex.h
index 627bdc0a0b41..18cd88204141 100644
--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -1758,7 +1758,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	     = regex_constants::format_default) const
       {
         string_type __result;
-        format(std::back_inserter(__result), __fmt + __builtin_strlen(__fmt),
+        format(std::back_inserter(__result),
+               __fmt + char_traits<char_type>::length(__fmt),
                __flags);
         return __result;
       }