Index: boost/lambda/detail/lambda_functor_base.hpp
===================================================================
--- boost/lambda/detail/lambda_functor_base.hpp	(revision 50249)
+++ boost/lambda/detail/lambda_functor_base.hpp	(working copy)
@@ -36,7 +36,7 @@
   explicit identity(par_t t) : elem(t) {}
 
   template <typename SigArgs> 
-  struct sig { typedef element_t type; };
+  struct sig { typedef typename boost::remove_const<element_t>::type type; };
 
   template<class RET, CALL_TEMPLATE_ARGS>
   RET call(CALL_FORMAL_ARGS) const { CALL_USE_ARGS; return elem; }