diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 6a5275d8..2ac8eacb 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -323,7 +323,7 @@ module ActiveModel
     # Returns a json representation of the serializable
     # object including the root.
     def as_json(args={})
-      super(root: args.fetch(:root, options.fetch(:root, root_name)))
+      super(:root => args.fetch(:root, options.fetch(:root, root_name)))
     end
 
     def serialize_object