diff --git a/include/boost/pending/ct_if.hpp b/include/boost/pending/ct_if.hpp
index 29fdbc4..2f8540d 100644
--- a/include/boost/pending/ct_if.hpp
+++ b/include/boost/pending/ct_if.hpp
@@ -19,13 +19,12 @@
   problem.
 */
 
+#include <boost/type_traits/integral_constant.hpp> // true_type and false_type
+
 namespace boost {
 
   struct ct_if_error { };
 
-  struct true_type { enum { value = true }; };
-  struct false_type { enum { value = false }; };
-
   template <class A, class B>
   struct ct_and { typedef false_type type; };
   template <> struct ct_and<true_type,true_type> { typedef true_type type; };