diff --git a/library/core/src/marker/variance.rs b/library/core/src/marker/variance.rs
index 31e30a16d45a3..9e135e89c451e 100644
--- a/library/core/src/marker/variance.rs
+++ b/library/core/src/marker/variance.rs
@@ -234,6 +234,7 @@ phantom_type! {
 }
 
 mod private_items {
+    #[unstable(feature = "std_internals", issue = "none")]
     pub trait PrivateItems {
         const VALUE: Self;
     }