2 files changed, 7 insertions, 2 deletions
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 8515ab45de2..093697a290c 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1041,8 +1041,11 @@ fn find_vtable_types_for_unsizing<'tcx>(
     match (source_ty.kind(), target_ty.kind()) {
         (&ty::Ref(_, a, _), &ty::Ref(_, b, _) | &ty::RawPtr(b, _))
         | (&ty::RawPtr(a, _), &ty::RawPtr(b, _)) => ptr_vtable(a, b),
-        (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
-            ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
+        (_, _)
+            if let Some(source_boxed) = source_ty.boxed_ty()
+                && let Some(target_boxed) = target_ty.boxed_ty() =>
+        {
+            ptr_vtable(source_boxed, target_boxed)
         }
 
         // T as dyn* Trait
diff --git a/compiler/rustc_monomorphize/src/lib.rs b/compiler/rustc_monomorphize/src/lib.rs
index b22e8e30465..91101ddd590 100644
--- a/compiler/rustc_monomorphize/src/lib.rs
+++ b/compiler/rustc_monomorphize/src/lib.rs
@@ -1,5 +1,7 @@
 // tidy-alphabetical-start
 #![feature(array_windows)]
+#![feature(if_let_guard)]
+#![feature(let_chains)]
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end