diff --git a/runtime/gc/reference_queue.h b/runtime/gc/reference_queue.h
index c45be85..7d9ddf6 100644
--- a/runtime/gc/reference_queue.h
+++ b/runtime/gc/reference_queue.h
@@ -36,6 +36,10 @@
 
 namespace gc {
 
+namespace collector {
+class GarbageCollector;
+}  // namespace collector
+
 class Heap;
 
 // Used to temporarily store java.lang.ref.Reference(s) during GC and prior to queueing on the
@@ -65,20 +69,19 @@
   // Enqueues finalizer references with white referents.  White referents are blackened, moved to
   // the zombie field, and the referent field is cleared.
   void EnqueueFinalizerReferences(ReferenceQueue* cleared_references,
-                                  IsHeapReferenceMarkedCallback* is_marked_callback,
-                                  MarkObjectCallback* mark_object_callback, void* arg)
+                                  collector::GarbageCollector* collector)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Walks the reference list marking any references subject to the reference clearing policy.
   // References with a black referent are removed from the list.  References with white referents
   // biased toward saving are blackened and also removed from the list.
-  void ForwardSoftReferences(IsHeapReferenceMarkedCallback* preserve_callback, void* arg)
+  void ForwardSoftReferences(MarkObjectVisitor* visitor)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Unlink the reference list clearing references objects with white referents. Cleared references
   // registered to a reference queue are scheduled for appending by the heap worker thread.
   void ClearWhiteReferences(ReferenceQueue* cleared_references,
-                            IsHeapReferenceMarkedCallback* is_marked_callback, void* arg)
+                            collector::GarbageCollector* collector)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void Dump(std::ostream& os) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -95,7 +98,7 @@
   }
 
   // Visits list_, currently only used for the mark compact GC.
-  void UpdateRoots(IsMarkedCallback* callback, void* arg)
+  void UpdateRoots(IsMarkedVisitor* visitor)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
  private: