diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index a838ba009b484..b96deb6a30e6d 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -681,6 +681,7 @@ impl<T> [T] {
     #[must_use]
     #[track_caller]
     #[rustc_const_unstable(feature = "const_index", issue = "143775")]
+    #[rustc_no_writable]
     pub const unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output
     where
         I: [const] SliceIndex<Self>,