Efficient looping through AS3 dictionary

for (var k in dictionary) 
{
  var key:KeyType = KeyType(k);
  var value:ValType = ValType(dictionary[k]); // <-- lookup
  // do stuff
}

This is what I use to loop through the entries in a dictionary. As you can see in every iteration I perform a lookup in the dictionary. Is there a more efficient way of iterating the dictionary (while keeping access to the key)?