diff --git a/src/libstd/thunk.rs b/src/libstd/thunk.rs
index 084893314a8..f1dc91f135f 100644
--- a/src/libstd/thunk.rs
+++ b/src/libstd/thunk.rs
@@ -11,6 +11,7 @@
 // Because this module is temporary...
 #![allow(missing_docs)]
 #![unstable(feature = "thunk")]
+#![deprecated(since = "1.2.0", reason = "use FnBox instead")]
 
 use alloc::boxed::{Box, FnBox};
 use core::marker::Send;