diff --git a/include/boost/range/adaptor/adjacent_filtered.hpp b/include/boost/range/adaptor/adjacent_filtered.hpp
index 287a4ae..405fe7b 100644
--- a/include/boost/range/adaptor/adjacent_filtered.hpp
+++ b/include/boost/range/adaptor/adjacent_filtered.hpp
@@ -181,7 +181,7 @@ namespace boost
         }
 
         template< class ForwardRng, class BinPredicate >
-        inline adjacent_filtered_range<BinPredicate, ForwardRng, false>
+        inline adjacent_filtered_range<BinPredicate, const ForwardRng, false>
         operator|( const ForwardRng& r,
                    const adjacent_excl_holder<BinPredicate>& f )
         {