diff --git a/build/vc100/turtle_test.vcxproj b/build/vc100/turtle_test.vcxproj
index bb5b6d6..72ab186 100644
--- a/build/vc100/turtle_test.vcxproj
+++ b/build/vc100/turtle_test.vcxproj
@@ -20,6 +20,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\..\test\mock_error.hpp" />
+    <ClInclude Include="..\..\test\undefined.hpp" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="..\..\test\detail\test_function.cpp" />
@@ -36,6 +37,7 @@
     <ClCompile Include="..\..\test\test_mock.cpp" />
     <ClCompile Include="..\..\test\test_object.cpp" />
     <ClCompile Include="..\..\test\test_sequence.cpp" />
+    <ClCompile Include="..\..\test\undefined.cpp" />
   </ItemGroup>
   <PropertyGroup Label="Globals">
     <ProjectGuid>{74810A2A-33D8-47D6-9A50-71261F1683F5}</ProjectGuid>
diff --git a/build/vc100/turtle_test.vcxproj.filters b/build/vc100/turtle_test.vcxproj.filters
index 5a0a82d..9d769d5 100644
--- a/build/vc100/turtle_test.vcxproj.filters
+++ b/build/vc100/turtle_test.vcxproj.filters
@@ -13,6 +13,9 @@
     <ClInclude Include="..\..\test\mock_error.hpp">
       <Filter>Source Files</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\test\undefined.hpp">
+      <Filter>Source Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="..\..\test\test_constraints.cpp">
@@ -57,5 +60,8 @@
     <ClCompile Include="..\..\test\test_matcher.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\test\undefined.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/test/detail/test_function.cpp b/test/detail/test_function.cpp
index c08cdf5..bd30f5a 100644
--- a/test/detail/test_function.cpp
+++ b/test/detail/test_function.cpp
@@ -8,6 +8,7 @@
 
 #define BOOST_AUTO_TEST_MAIN
 #include "../mock_error.hpp"
+#include "../undefined.hpp"
 #include <turtle/detail/function.hpp>
 #include <turtle/constraints.hpp>
 #include <boost/test/auto_unit_test.hpp>
@@ -533,6 +534,20 @@ BOOST_FIXTURE_TEST_CASE( triggering_an_expectation_returns_the_set_auto_ptr_valu
         BOOST_CHECK_NO_THROW( f() );
         CHECK_CALLS( 1 );
     }
+}
+
+BOOST_FIXTURE_TEST_CASE( triggering_an_expectation_returns_the_set_shared_ptr_value, error_fixture )
+{
+    {
+        mock::detail::function< boost::shared_ptr< A >() > f;
+        f.expect().returns( new B );
+        BOOST_CHECK_NO_THROW( f() );
+        CHECK_CALLS( 1 );
+    }
+}
+
+BOOST_FIXTURE_TEST_CASE( triggering_an_expectation_returns_by_reference, error_fixture )
+{
     {
         mock::detail::function< A&() > f;
         B b;
@@ -547,6 +562,11 @@ BOOST_FIXTURE_TEST_CASE( triggering_an_expectation_returns_the_set_auto_ptr_valu
         BOOST_CHECK_NO_THROW( f() );
         CHECK_CALLS( 1 );
     }
+    {
+        mock::detail::function< undefined&() > f;
+        f.expect().returns( boost::ref( get_undefined() ) );
+        f.reset();
+    }
 }
 
 namespace
diff --git a/test/test_integration.cpp b/test/test_integration.cpp
index db47626..de9b85c 100644
--- a/test/test_integration.cpp
+++ b/test/test_integration.cpp
@@ -7,6 +7,7 @@
 // http://www.boost.org/LICENSE_1_0.txt)
 
 #include "mock_error.hpp"
+#include "undefined.hpp"
 #include <turtle/mock.hpp>
 #include <boost/test/auto_unit_test.hpp>
 #include <boost/noncopyable.hpp>
@@ -128,17 +129,15 @@ BOOST_AUTO_TEST_CASE( mock_object_method_const_disambiguation )
 
 namespace
 {
-    struct my_declared_but_undefined_type;
-
-    MOCK_CLASS( my_declared_but_undefined_mock )
+    MOCK_CLASS( my_undefined_mock )
     {
-        MOCK_METHOD_EXT( m, 1, void( my_declared_but_undefined_type& ), t )
+        MOCK_METHOD_EXT( m, 1, void( undefined& ), t )
     };
 }
 
 BOOST_AUTO_TEST_CASE( mock_object_method_with_declared_but_not_defined_parameter_is_valid )
 {
-    my_declared_but_undefined_mock mock;
+    my_undefined_mock mock;
     MOCK_EXPECT( mock.t );
 }
 
diff --git a/test/undefined.cpp b/test/undefined.cpp
new file mode 100644
index 0000000..9855cbb
--- /dev/null
+++ b/test/undefined.cpp
@@ -0,0 +1,18 @@
+// http://turtle.sourceforge.net
+//
+// Copyright Mathieu Champlon 2013
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#include "undefined.hpp"
+
+struct undefined
+{};
+
+undefined& get_undefined()
+{
+    static undefined u;
+    return u;
+}
diff --git a/test/undefined.hpp b/test/undefined.hpp
new file mode 100644
index 0000000..f2418c0
--- /dev/null
+++ b/test/undefined.hpp
@@ -0,0 +1,16 @@
+// http://turtle.sourceforge.net
+//
+// Copyright Mathieu Champlon 2013
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef MOCK_TEST_UNDEFINED_HPP_INCLUDED
+#define MOCK_TEST_UNDEFINED_HPP_INCLUDED
+
+struct undefined;
+
+undefined& get_undefined();
+
+#endif // MOCK_TEST_UNDEFINED_HPP_INCLUDED
diff --git a/turtle/detail/action.hpp b/turtle/detail/action.hpp
index ddfde74..f3447d4 100644
--- a/turtle/detail/action.hpp
+++ b/turtle/detail/action.hpp
@@ -12,9 +12,7 @@
 #include "../config.hpp"
 #include "lambda.hpp"
 #include <boost/type_traits/remove_reference.hpp>
-#include <boost/type_traits/is_convertible.hpp>
 #include <boost/type_traits/remove_const.hpp>
-#include <boost/utility/enable_if.hpp>
 #include <boost/make_shared.hpp>
 #include <boost/function.hpp>
 #include <boost/ref.hpp>
@@ -37,26 +35,19 @@ namespace detail
 
     public:
         template< typename Value >
-        void returns( Value v,
-            BOOST_DEDUCED_TYPENAME boost::enable_if<
-                boost::is_convertible< Value, result_type > >::type* = 0 )
+        void returns( Value v )
+        {
+            r_ = boost::make_shared< Value >( v );
+            f_ = lambda_type::make_val( boost::ref( *r_ ) );
+        }
+        template< typename Value >
+        void returns( Value* v )
         {
             r_ = boost::make_shared< result_type >( v );
             f_ = lambda_type::make_val( boost::ref( *r_ ) );
         }
-        template< typename Value >
-        void returns( Value v,
-            BOOST_DEDUCED_TYPENAME boost::disable_if<
-                boost::is_convertible< Value, result_type > >::type* = 0 )
-        {
-            // if an error is generated by the line below it means a value
-            // passed to 'returns' was of the wrong type as it cannot be
-            // used to copy construct a Result
-            r_ = boost::make_shared< Value >( v );
-            f_ = lambda_type::make_val( boost::ref( *r_ ) );
-        }
         template< typename Y >
-        void returns( boost::reference_wrapper< Y > r )
+        void returns( const boost::reference_wrapper< Y >& r )
         {
             f_ = lambda_type::make_val( r );
         }
@@ -98,7 +89,7 @@ namespace detail
             f_ = lambda_type::make_val( r );
         }
         template< typename Y >
-        void returns( boost::reference_wrapper< Y > r )
+        void returns( const boost::reference_wrapper< Y >& r )
         {
             f_ = lambda_type::make_val( r );
         }
@@ -211,7 +202,7 @@ namespace detail
             f_ = lambda_type::make_val( boost::ref( r_ ) );
         }
         template< typename Y >
-        void set( boost::reference_wrapper< Y > r )
+        void set( const boost::reference_wrapper< Y >& r )
         {
             f_ = lambda_type::make_val( r );
             r_.reset();