diff --git a/runtime/base/arena_containers.h b/runtime/base/arena_containers.h
index a7aafdf..810c1c4 100644
--- a/runtime/base/arena_containers.h
+++ b/runtime/base/arena_containers.h
@@ -76,6 +76,7 @@
 class ArenaAllocatorAdapterKindImpl {
  public:
   explicit ArenaAllocatorAdapterKindImpl(ArenaAllocKind kind) : kind_(kind) { }
+  ArenaAllocatorAdapterKindImpl(const ArenaAllocatorAdapterKindImpl&) = default;
   ArenaAllocatorAdapterKindImpl& operator=(const ArenaAllocatorAdapterKindImpl&) = default;
   ArenaAllocKind Kind() { return kind_; }