diff --git a/include/boost/python/detail/enable_if.hpp b/include/boost/python/detail/enable_if.hpp
index 247b06f2..e9f2a823 100755
--- a/include/boost/python/detail/enable_if.hpp
+++ b/include/boost/python/detail/enable_if.hpp
@@ -24,13 +24,13 @@ struct disable_if_arg
     typedef typename mpl::if_<C,int&,T>::type type;
 };
              
-template <class C, class T>
+template <class C, class T = void>
 struct enable_if_ret
 {
     typedef typename mpl::if_<C,T,int[2]>::type type;
 };
              
-template <class C, class T>
+template <class C, class T = void>
 struct disable_if_ret
 {
     typedef typename mpl::if_<C,int[2],T>::type type;
@@ -43,22 +43,22 @@ struct disable_if_ret
 
 namespace boost { namespace python { namespace detail { 
 
-template <class C, class T>
+template <class C, class T = int>
 struct enable_if_arg
   : enable_if<C,T>
 {};
              
-template <class C, class T>
+template <class C, class T = int>
 struct disable_if_arg
   : disable_if<C,T>
 {};
              
-template <class C, class T>
+template <class C, class T = void>
 struct enable_if_ret
   : enable_if<C,T>
 {};
              
-template <class C, class T>
+template <class C, class T = void>
 struct disable_if_ret
   : disable_if<C,T>
 {};