Querying

I'm having trouble querying by columns that use Timex.Ecto.DateTime. Is there something I'm doing wrong?

``` elixir
> {:ok, start_date} = DateFormat.parse("2015-10-01", "{YYYY}-{0M}-{0D}")
> Repo.all(from p in Post, where: v.submitted_at > ^start_date)

** (UndefinedFunctionError) undefined function: Timex.DateTime.type/0
(ecto) lib/ecto/query/planner.ex:124: Ecto.Query.Planner.prepare/3
(ecto) lib/ecto/query/planner.ex:66: Ecto.Query.Planner.query/4
(ecto) lib/ecto/repo/queryable.ex:91: Ecto.Repo.Queryable.execute/5
(ecto) lib/ecto/repo/queryable.ex:15: Ecto.Repo.Queryable.all/4
```