to_json on ActiveRecord::Relation throws CircularReference Exception

In my controller I'm querying a table using an ActiveRecord model and trying to return json.
When I attempt to call to_json on an ActiveRecord::Relation, I get a circular reference exception. When I call to_a on the relation and THEN call to_json, it works.

Code that fails:

Model.where().to_json

Code that works

Model.where().to_a.to_json

This is reproducable on the rails console.

Is this expected? It seems wrong/non-discoverable if it is.