diff --git a/src/libraries/turtle/is_functor.hpp b/src/libraries/turtle/is_functor.hpp
index 1c8e53e..e00791f 100644
--- a/src/libraries/turtle/is_functor.hpp
+++ b/src/libraries/turtle/is_functor.hpp
@@ -20,7 +20,7 @@ namespace detail
     typedef char true_type;
     struct false_type
     {
-       char padding[8];
+       true_type padding[2];
     };
 
     template< typename T >
diff --git a/src/tests/turtle_test/is_functor_test.cpp b/src/tests/turtle_test/is_functor_test.cpp
index ce83c43..dd511fe 100644
--- a/src/tests/turtle_test/is_functor_test.cpp
+++ b/src/tests/turtle_test/is_functor_test.cpp
@@ -23,6 +23,8 @@
 
 namespace
 {
+    BOOST_STATIC_ASSERT( sizeof( mock::detail::true_type ) != sizeof( mock::detail::false_type ) );
+
     template< typename T >
     void check( T )
     {