diff --git a/src/monomorphize_collector.rs b/src/monomorphize_collector.rs
index 4deedb7..1cdf722 100644
--- a/src/monomorphize_collector.rs
+++ b/src/monomorphize_collector.rs
@@ -1179,8 +1179,8 @@ fn collect_alloc<'tcx>(
             trace!("collecting {:?} with {:#?}", alloc_id, instance);
             output.push(create_fn_mono_item(tcx, instance, DUMMY_SP));
         }
-        GlobalAlloc::VTable(ty, trait_ref) => {
-            let alloc_id = tcx.vtable_allocation((ty, trait_ref));
+        GlobalAlloc::VTable(ty, dyn_ty) => {
+            let alloc_id = tcx.vtable_allocation((ty, dyn_ty.principal()));
             collect_alloc(tcx, alloc_id, output)
         }
     }
diff --git a/src/preempt_count/check.rs b/src/preempt_count/check.rs
index 2ab7ef6..3c1b366 100644
--- a/src/preempt_count/check.rs
+++ b/src/preempt_count/check.rs
@@ -215,8 +215,8 @@ impl<'mir, 'tcx, 'cx> MirNeighborVisitor<'mir, 'tcx, 'cx> {
             GlobalAlloc::Function { instance, .. } => {
                 self.check_fn_pointer_cast(instance, span)?;
             }
-            GlobalAlloc::VTable(ty, trait_ref) => {
-                self.check_vtable_construction(ty, trait_ref, span)?;
+            GlobalAlloc::VTable(ty, dyn_ty) => {
+                self.check_vtable_construction(ty, dyn_ty.principal(), span)?;
             }
         }