diff --git a/library/std/src/sync/mpsc/mod.rs b/library/std/src/sync/mpsc/mod.rs
index 0e0c87d1c74..71ff4237d00 100644
--- a/library/std/src/sync/mpsc/mod.rs
+++ b/library/std/src/sync/mpsc/mod.rs
@@ -347,8 +347,8 @@ pub struct Sender<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: Send> Send for Sender<T> {}
 
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> !Sync for Sender<T> {}
+#[stable(feature = "mpsc_sender_sync", since = "CURRENT_RUSTC_VERSION")]
+unsafe impl<T: Send> Sync for Sender<T> {}
 
 /// The sending-half of Rust's synchronous [`sync_channel`] type.
 ///