Index: boost/fusion/adapted/boost_tuple/detail/size_impl.hpp
===================================================================
--- boost/fusion/adapted/boost_tuple/detail/size_impl.hpp	(revision 51856)
+++ boost/fusion/adapted/boost_tuple/detail/size_impl.hpp	(working copy)
@@ -9,6 +9,7 @@
 
 #include <boost/tuple/tuple.hpp>
 #include <boost/mpl/int.hpp>
+#include <boost/type_traits/remove_const.hpp>
 
 namespace boost { namespace fusion 
 {
@@ -23,7 +24,7 @@
         struct size_impl<boost_tuple_tag>
         {
             template <typename Sequence>
-            struct apply : mpl::int_<tuples::length<Sequence>::value> {};
+            struct apply : mpl::int_<tuples::length<typename boost::remove_const<Sequence>::type>::value> {};
         };
     }
 }}