diff --git a/include/boost/detail/utf8_codecvt_facet.hpp b/include/boost/detail/utf8_codecvt_facet.hpp
index 97e6ddc..936bb9d 100644
--- a/include/boost/detail/utf8_codecvt_facet.hpp
+++ b/include/boost/detail/utf8_codecvt_facet.hpp
@@ -162,7 +162,7 @@ protected:
     virtual std::codecvt_base::result do_unshift(
         std::mbstate_t&,
         char * from,
-        char * to,
+        char * /*to*/,
         char * & next
     ) const 
     {
diff --git a/utf8_codecvt_facet.cpp b/utf8_codecvt_facet.cpp
index f271cdb..20d79de 100644
--- a/utf8_codecvt_facet.cpp
+++ b/utf8_codecvt_facet.cpp
@@ -32,7 +32,7 @@ BOOST_UTF8_BEGIN_NAMESPACE
 
 // Translate incoming UTF-8 into UCS-4
 std::codecvt_base::result utf8_codecvt_facet::do_in(
-    std::mbstate_t& state, 
+    std::mbstate_t& /*state*/, 
     const char * from,
     const char * from_end, 
     const char * & from_next,
@@ -109,7 +109,7 @@ std::codecvt_base::result utf8_codecvt_facet::do_in(
 }
 
 std::codecvt_base::result utf8_codecvt_facet::do_out(
-    std::mbstate_t& state, 
+    std::mbstate_t& /*state*/, 
     const wchar_t *   from,
     const wchar_t * from_end, 
     const wchar_t * & from_next,