diff --git a/include/__memory/unique_ptr.h b/include/__memory/unique_ptr.h
index a505dab..327e02c 100644
--- a/include/__memory/unique_ptr.h
+++ b/include/__memory/unique_ptr.h
@@ -41,6 +41,7 @@
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <cstddef>
+#include <stlfwd>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -122,7 +123,7 @@ struct __unique_ptr_deleter_sfinae<_Deleter&> {
 #  define _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI
 #endif
 
-template <class _Tp, class _Dp = default_delete<_Tp> >
+template <class _Tp, class _Dp>
 class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr {
 public:
   typedef _Tp element_type;