Is it bad design to call Grails services from domain objects?

As I've been using Grails more and more, I find myself writing code in multiple controllers that really seems like it should be part of a domain class. Sometimes, this domain code contains a call to a service class. For example, I recently wrote a domain method that looked something like this:

class Purchase {

    // Injected
    def paymentService

    String captureTransactionId
    Boolean captured

    // ...

    def capture() {
        captureTransactionId = paymentService.capturePurchase( this )
        captured = captureTransactionId != null
    }

I don't feel outright dirty writing this code, but I haven't made a study of best design practices in Grails, so I wanted to get some opinions.