diff --git a/src/unsize.rs b/src/unsize.rs
index 4acbc8a27ed..967aa53abbd 100644
--- a/src/unsize.rs
+++ b/src/unsize.rs
@@ -39,8 +39,7 @@ pub(crate) fn unsized_info<'tcx>(
             }
 
             // trait upcasting coercion
-            let vptr_entry_idx =
-                fx.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((source, target));
+            let vptr_entry_idx = fx.tcx.supertrait_vtable_slot((source, target));
 
             if let Some(entry_idx) = vptr_entry_idx {
                 let entry_idx = u32::try_from(entry_idx).unwrap();