Stubbing after stubbing in Spock 0.7-groovy-2.0

package com.example

import spock.lang.Ignore
import spock.lang.Specification

class StubAfterStubSpec extends Specification {

    private static final DEFAULT_STUBBING = 42
    
    def stub
    
    def setup() {
        stub = Stub(java.util.concurrent.Callable)
        stub.call() >> 42
    }
    
    def "should return the value stubbed in setup"() {
        expect:
        stub.call() == DEFAULT_STUBBING
    }
    
    @Ignore('Nah, wont work :(')
    def "should redefine the stub's response"() {
        given:
        def overriddenStubbing = 43
        stub.call() >> overriddenStubbing

        when:
        def result = stub.call()

        then:
        result == overriddenStubbing
    }
    
    def "should redefine the stub's response in then: block"() {
        given:
        def overriddenStubbing = 43
        
        when:
        def result = stub.call()
        
        then:
        stub.call() >> overriddenStubbing
        result == overriddenStubbing
    }
}

Thanks that's exactly what I wanted to know. :-)