diff --git a/src/libraries/turtle/is_serializable.hpp b/src/libraries/turtle/is_serializable.hpp
index f499026..511ad7b 100644
--- a/src/libraries/turtle/is_serializable.hpp
+++ b/src/libraries/turtle/is_serializable.hpp
@@ -10,7 +10,6 @@
 #define MOCK_IS_SERIALIZABLE_HPP_INCLUDED
 
 #include "yes_no_type.hpp"
-#include "sink.hpp"
 #include <boost/mpl/bool.hpp>
 
 #ifdef _MSC_VER
@@ -24,17 +23,14 @@ namespace detail
 {
 namespace serializable
 {
-    template< typename S >
-    yes_type operator<<( S&, sink );
+    template< typename S, typename T >
+    yes_type operator<<( S&, const T& );
 
     template< typename S, typename T >
     struct impl
     {
         static S* s;
         static T* t;
-        // if an error is generated by the line below it means T has more than
-        // one conversion to other types which are serializable : the easiest
-        // solution would be to add a format function for T.
         enum { value = sizeof( yes_type(), (*s << *t), yes_type() ) == sizeof( yes_type ) };
     };
 }
diff --git a/src/tests/turtle_test/is_serializable_test.cpp b/src/tests/turtle_test/is_serializable_test.cpp
index dffef36..8637c7f 100644
--- a/src/tests/turtle_test/is_serializable_test.cpp
+++ b/src/tests/turtle_test/is_serializable_test.cpp
@@ -60,7 +60,7 @@ namespace
     };
 }
 
-BOOST_MPL_ASSERT(( mock::detail::is_serializable< std::ostream, convertible_to_base > ));
+BOOST_MPL_ASSERT_NOT(( mock::detail::is_serializable< std::ostream, convertible_to_base > ));
 
 namespace
 {
@@ -80,7 +80,7 @@ namespace
     };
 }
 
-BOOST_MPL_ASSERT(( mock::detail::is_serializable< std::ostream, convertible_to_serializable > ));
+BOOST_MPL_ASSERT_NOT(( mock::detail::is_serializable< std::ostream, convertible_to_serializable > ));
 
 namespace
 {
@@ -88,4 +88,4 @@ namespace
     {};
 }
 
-BOOST_MPL_ASSERT(( mock::detail::is_serializable< std::ostream, derived_from_serializable > ));
+BOOST_MPL_ASSERT_NOT(( mock::detail::is_serializable< std::ostream, derived_from_serializable > ));