my view generates keys in this format

["job_id:1234567890", 1271430291000]

where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1

and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now

function(keys,values,rereduce)
{ 
  var now = new Date().valueOf();
  var first = Number.MIN_VALUE;
  var last = Number.MAX_VALUE;
  if (rereduce)
  {
    first = Math.max(first,values[0].first);
    last = Math.min(last,values[0].last);  
  }
  else
  {
    first = keys[0][0][1];
    last = keys[keys.length-1][0][1];
  }
  return {first:now - first, last:now - last};
}

and when processing a query it constantly raises the following execption:

function raised exception (new TypeError("keys has no properties", "", 1))

I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?