var references in groovy closures

//slaves
def machines = ['a', 'b', 'c']

//container
def ds = [:]

for (machine in machines) {
        //prints "Adding entry a\n...Adding entry b\n..." as expected
        print("Adding entry for: " + machine);

        ds[machine] = {download_builds( machine )}; //entry is added, apparently.
    }

//execute all closures in hash ds concurrently
parallel ds;

//They all execute download_builds('c'); ... ?  Because the last assignment made to 'machine' was 'c'?