Mongo db input / output when running convertToCapped

gistfile1.js

  // create a db instance via driver
  var db = new Db(self.database, serverConnection, dbOptions);

  db.open(function(err, _db){
     // works fine
  }

  db.command({"convertToCapped": collectionName, size: collOptions.size}, 
     function(err, result){
                console.log('err', err)
                console.log('result', result)
     }
  )

// Returns the following output:
// err null
// result { errmsg: 'cloneCollectionAsCapped failed: { errmsg: "exception: source collection 507-test.queue does not exist", code: 10301, ok: 0.0 }',  ok: 0 }


// Expected Result:
// err {errmsg: ...}
// result null