"Single instance component" is instanced second time by child

Symptom:

"A" - is singleton object (singe instance component)

Code:
PlexusContainer container=new DefaultPlexusContainer();
container.lookup("A").
container.createChildContainer("A",Collections.EMPTY_LIST,Collections.EMPTY_MAP, Collections.EMPTY_LIST).lookup("A").

The components "A" is instanced twice.

Unit test for plexus container is attached to the bug.
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Explanation:

createChildContainer method calls initializeConfiguration that uses PlexusXmlComponentDiscoverer to
merge the container configuration. The method parses META-INF/plexus/plexus.xml another time.
Using this configuration ComponentRepository for child-container is instanced. So the ComponentRepository starts with
preconfigured map (containing configuration for component "A").

Then child-container.lookups finds the component in child's componentRepository - so don't ask Parent's repository for component.

Changing line 1136 of Default plexus Container from
if (( !containerContext.contains( PlexusConstants.IGNORE_CONTAINER_CONFIGURATION )
to
if ((parentContainer==null)&&( !containerContext.contains( PlexusConstants.IGNORE_CONTAINER_CONFIGURATION )

correct's the problem.

I don't know (and there is no documentation), what the correct plexus's behavior should be. How should work child container with configuration.