GrailsDomainClassProperty.isAssociation() returns true for types mapped with Hibernate UserTypes

When a domain class has a field mapped by a UserType GrailsDomainClassProperty.isAssociation() and isOneToOne() both return true. This is a problem with, for example, any class using joda-time properties, e.g.

class Person {
org.joda.time.LocalDate birthday
static mapping =

}

def app = org.codehaus.groovy.grails.commons.ApplicationHolder.application
def dc = app.getArtefact("Domain", "Person")
def prop = dc.getPropertyByName("birthday")
assert prop.type == org.joda.time.LocalDate
assert !prop.association // FAILS
assert !prop.oneToOne // FAILS

The main difficulty I've found that this causes is that list.gsp and show.gsp scaffolding templates have to be customised to handle these types otherwise Grails will try to render them as association properties and the scaffolding will crash.