Index: at_impl.hpp
===================================================================
--- at_impl.hpp	(revision 82093)
+++ at_impl.hpp	(working copy)
@@ -35,6 +35,7 @@
                 static type
                 call(Sequence& seq)
                 {
+                    BOOST_STATIC_ASSERT(((size_t)N::value < (size_t)Sequence::static_size));
                     return seq[N::value];
                 }
             };