Removing things from Context

I believe I am seeing a bug in Avalons DefaultContext.  When you try and remove
something from context by doing a context.put(key, null), the context class is
doing: 

    public void put( final Object key, final Object value )
        throws IllegalStateException
    {
        checkWriteable();
        if( null == value )
        {
            m_contextData.remove( key );
        }
        else
        {
            m_contextData.put( key, value );
        }
    }

However a context can have a parent context I guess, and its not going in there
to remove the value as it might be located there.  So I am seeing things not
get removed from session when I tell it to. 

Has anyone got a workaround for this, or know if there is an updated avalon with
this fix? 

Thank you, 
Nathan