Is const_cast(iterator->second) safe?

I want to know if this code is safe and doesnt have any undefined behavior.

 QueueMap::const_iterator it = m_3playersQueue.find(s->m_GameCode);
  if(it == m_3playersQueue.end())
  {
      std::deque<Session*> stack;
      stack.push_back(s);
 
      m_3playersQueue[s->m_GameCode] = stack;
      return;
  }
 
  const_cast<std::deque<Session*>&>(it->second).push_back(s);
 
  QueueMap is of type std::tr1::unordered_map< uint32, std::deque<Session*> >
 

Thanks

---