unregisterComponent fails after getComponentInstances

There seems to be something wrong with the component unregistration from DefaultPicoContainer. I've seen the testcase DefaultPicoContainerUnregisterComponentTestCase working correctly, but if I add the line:

picoContainer.getComponentInstances();

right before the picoContainer.unregisterComponent(..) into every test
method in this testcase, 3 of the 4 tests fail.

Some further investigation shows, that after calling getComponentInstances() and unregisterComponent() (in this order), getComponentKeys() will show the correct amount of keys, but getComponentInstances() will not (the latter will show the unregistered component as well), so that smells like inconsistent behaviour.

I think not being able to completely unregister components from picocontainer is a major issue, please investigate the problem.