How to handle Long and different formats in a Play! Scala form?

In my model all associated accounts are Long not normal integers. However, when handling the Scala form in the new Play! 2.0 I can only validate an Int number in a form and not a Long.

http://www.playframework.org/documentation/2.0/ScalaForms

Take the following form:

val clientForm: Form[Client] = Form(
    mapping(
      "id" -> number,
      "name" -> text(minLength = 4),
      "email" -> optional(text),
      "phone" -> optional(text),
      "address" -> text(minLength = 4),
      "city" -> text(minLength = 2),
      "province" -> text(minLength = 2),
      "account_id" -> number
    )
    (Client.apply)(Client.unapply)
  )

Where you see account_id I want to apply a Long, so how could I cast that in the simplest way possible? The Client.apply syntax is awesome for its simplicity but I'm open to options like mapping. Thanks!