diff --git a/libcxx/include/__bit_reference b/libcxx/include/__bit_reference
--- a/libcxx/include/__bit_reference
+++ b/libcxx/include/__bit_reference
@@ -62,6 +62,8 @@
         return *this;
     }
 
+    __bit_reference(const __bit_reference&) = default;
+
     _LIBCPP_INLINE_VISIBILITY
     __bit_reference& operator=(const __bit_reference& __x) _NOEXCEPT
         {return operator=(static_cast<bool>(__x));}
@@ -148,6 +150,7 @@
         : __seg_(__s), __mask_(__m) {}
 
     __bit_const_reference& operator=(const __bit_const_reference& __x);
+    __bit_const_reference(const __bit_const_reference&) = default;
 };
 
 // find