Groovy compilation error with Gradle source set

UserAccountRepositorySaveSpec.groovy

// reference to ComponentTestConfiguration results in a compilation error 
// whereas reference to IshouldBeCompiled is fine
    @ContextConfiguration(classes = [ComponentTestConfiguration.class])
    class UserAccountRepositorySaveSpec extends Specification {

        @Autowired
        UserAccountRepository repository

        def saveReturnsInstance() {
            given:
            def userName = randomAlphanumeric(new IshouldBeCompiled().configurationValue())
            def password = randomAlphanumeric(6)

            def userAccount = new UserAccount(userName, password)

            when:
            def savedUserAccount = repository.save(userAccount)

            then:
            savedUserAccount != null

        }
    }