StatefulSessionInstanceCache has ConcurrentHashMap entrySet problem

protected void removePassivated(long maxLifeAfterPassivation)
{
StatefulSessionPersistenceManager store = m_container.getPersistenceManager();
long now = System.currentTimeMillis();
log.debug("removePassivated, now="now", maxLifeAfterPassivation="+maxLifeAfterPassivation);
Iterator entries = passivatedIDs.entrySet().iterator();
while (entries.hasNext())
{
Map.Entry entry = (Map.Entry) entries.next();
Object key = entry.getKey();
long passivationTime = ((Long) entry.getValue()).longValue();

entry.getValue() could be null