withWindow() bug: Geb does not save/image the designated popped-up window #401

In my application, I have a 'main' page that pops up a window in which runs a Spring WebFlow flow.

I have a Geb/Spock test spec for this flow looking something like (slightly sanitized):

...
    def 'flow: A'() {
        expect:
            // all this is in the scripting window that opens automatically
            assert null == withWindow({ title.startsWith('A') }) {
                withConfirm(true) { $('form').button().click() }

                waitFor { title.startsWith('B') }
                $('form').with { f ->
                    f.streetName = 'fake'
                    f.streetType = 'St'
                    f._eventId_accept().click()
                }
            }
    }

    def "flow: C"() {
        expect:
            assert null == withWindow({ title.startsWith('C') }) {
                $('form').with { f ->
                    f._eventId_next().click()
                }
            }
    }
...

And so on (for test methods "flow: D", etc., etc.).

This all works very nicely; the flow is progressed properly and any errors (ie incorrect titles) detected correctly.

As is normal for Geb, at the end of each test, Geb stores a page into the reports dir together with a generated PNG of the page.

Here's the bug: Geb repeatedly saves/images of only the 'main' page. Geb does not save/image the popped-up window that was the actual 'focus' of withWindow().

This is regardless of whether or not the test method ended successfully or because of an error.

I am guessing that withWindow() fails to 'update' the reporting system (somehow...)?

I can work around this by manually placing "report '...'" instructions into each test but this is not particularly nice.

Using reportGroup does not affect this either...I end up with a separate directory full of identical screenshots of the main page.

I am seeing this with Java 1.8_60, Geb 0.12.2, driver is phantomJs 2.0, on Mac OSX.