diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 71b53cc88e54..bf7921ea1a2b 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -184,6 +184,7 @@ impl<T: ?Sized> Box<T> {
 
     #[unstable(feature = "ptr_internals", issue = "0", reason = "use into_raw_non_null instead")]
     #[inline]
+    #[doc(hidden)]
     pub fn into_unique(b: Box<T>) -> Unique<T> {
         let unique = b.0;
         mem::forget(b);