--- boost/chrono/duration.hpp
+++ boost/chrono/duration.hpp
@@ -663,36 +663,36 @@
     template <class LhsDuration, class RhsDuration>
     struct duration_eq
     {
-      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const RhsDuration& rhs)
+      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const RhsDuration& rhs) const
         {
             typedef typename common_type<LhsDuration, RhsDuration>::type CD;
             return CD(lhs).count() == CD(rhs).count();
         }
     };
 
     template <class LhsDuration>
     struct duration_eq<LhsDuration, LhsDuration>
     {
-      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const LhsDuration& rhs)
+      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const LhsDuration& rhs) const
         {
             return lhs.count() == rhs.count();
         }
     };
 
     template <class LhsDuration, class RhsDuration>
     struct duration_lt
     {
-      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const RhsDuration& rhs)
+      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const RhsDuration& rhs) const
         {
             typedef typename common_type<LhsDuration, RhsDuration>::type CD;
             return CD(lhs).count() < CD(rhs).count();
         }
     };
 
     template <class LhsDuration>
     struct duration_lt<LhsDuration, LhsDuration>
     {
-      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const LhsDuration& rhs)
+      BOOST_CONSTEXPR bool operator()(const LhsDuration& lhs, const LhsDuration& rhs) const
         {
             return lhs.count() < rhs.count();
         }