2 files changed, 3 insertions, 1 deletions
diff --git a/compiler/rustc_smir/src/lib.rs b/compiler/rustc_smir/src/lib.rs
index 771ff98d58d..63623cfad72 100644
--- a/compiler/rustc_smir/src/lib.rs
+++ b/compiler/rustc_smir/src/lib.rs
@@ -9,6 +9,7 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![allow(rustc::usage_of_ty_tykind)]
+#![cfg_attr(not(bootstrap), feature(sized_hierarchy))]
 #![doc(
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
     test(attr(allow(unused_variables), deny(warnings)))
diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index b5003baaf63..64fe181c26d 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -9,6 +9,7 @@
 
 use std::ops::RangeInclusive;
 
+use rustc_data_structures::PointeeSized;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::AllocId;
@@ -158,7 +159,7 @@ pub(crate) fn new_item_kind(kind: DefKind) -> ItemKind {
 }
 
 /// Trait used to convert between an internal MIR type to a Stable MIR type.
-pub trait Stable<'cx> {
+pub trait Stable<'cx>: PointeeSized {
     /// The stable representation of the type implementing Stable.
     type T;
     /// Converts an object to the equivalent Stable MIR representation.