diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 5f47dcdbf99..470818d0d29 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,9 @@
 2016-04-18  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/bits/locale_facets.h (ctype::do_narrow): Add attribute to
+	unused parameter.
+	* include/bits/regex_automaton.h (_NFA::_M_insert_alt): Likewise.
+
 	* include/ext/string_conversions.h (__stoa): Avoid -Wsign-compare
 	warnings.
 
diff --git a/libstdc++-v3/include/bits/locale_facets.h b/libstdc++-v3/include/bits/locale_facets.h
index e3e206b7d49..eda07b64e1c 100644
--- a/libstdc++-v3/include/bits/locale_facets.h
+++ b/libstdc++-v3/include/bits/locale_facets.h
@@ -1128,7 +1128,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *  @return  The converted char.
       */
       virtual char
-      do_narrow(char_type __c, char __dfault) const
+      do_narrow(char_type __c, char __dfault __attribute__((__unused__))) const
       { return __c; }
 
       /**
@@ -1155,7 +1155,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       */
       virtual const char_type*
       do_narrow(const char_type* __lo, const char_type* __hi,
-		char __dfault, char* __to) const
+		char __dfault __attribute__((__unused__)), char* __to) const
       {
 	__builtin_memcpy(__to, __lo, __hi - __lo);
 	return __hi;
diff --git a/libstdc++-v3/include/bits/regex_automaton.h b/libstdc++-v3/include/bits/regex_automaton.h
index 07158c4926b..c29fbd9ab12 100644
--- a/libstdc++-v3/include/bits/regex_automaton.h
+++ b/libstdc++-v3/include/bits/regex_automaton.h
@@ -241,7 +241,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       }
 
       _StateIdT
-      _M_insert_alt(_StateIdT __next, _StateIdT __alt, bool __neg)
+      _M_insert_alt(_StateIdT __next, _StateIdT __alt,
+		    bool __neg __attribute__((__unused__)))
       {
 	_StateT __tmp(_S_opcode_alternative);
 	// It labels every quantifier to make greedy comparison easier in BFS