diff --git a/include/xo/refcnt/Refcounted.hpp b/include/xo/refcnt/Refcounted.hpp
index 0b62e557..33c5b377 100644
--- a/include/xo/refcnt/Refcounted.hpp
+++ b/include/xo/refcnt/Refcounted.hpp
@@ -257,6 +257,8 @@ namespace xo {
         template<typename T>
         class Borrow {
         public:
+            Borrow() = default;
+
             template <typename S>
             Borrow(rp<S> const & x) : ptr_(x.get()) {}