diff --git a/src/reference_table.h b/src/reference_table.h
index 28af887..de9d45d 100644
--- a/src/reference_table.h
+++ b/src/reference_table.h
@@ -43,13 +43,14 @@
 
   size_t Size() const;
 
-  void Dump(std::ostream& os) const;
+  void Dump(std::ostream& os) const SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
 
   void VisitRoots(Heap::RootVisitor* visitor, void* arg);
 
  private:
   typedef std::vector<const Object*> Table;
-  static void Dump(std::ostream& os, const Table& entries);
+  static void Dump(std::ostream& os, const Table& entries)
+      SHARED_LOCKS_REQUIRED(GlobalSynchronization::mutator_lock_);
   friend class IndirectReferenceTable; // For Dump.
 
   std::string name_;