When using a join and giving an alias to each select column the hyrdrator only returns one row.

Hi All
I am running into a strange problem using Doctrine-1.2.2-- I have a multi row result set but only the first row of it is returned in the hyrdated array that is generated.
I have tracked this down in the code to get a basic idea of whats going on – it seems that the $id variable in the hydrateResultSet function in Doctrine_Hydrator_Graph isn't being populated properly with data about the fields that are returning from my query. The _gatherRowData function seems to never detect that one of my columns is an identifier ("if ($cache[$key]['isIdentifier'])

$q = Doctrine_Query::create();
$q->from('Customer Customer');
$q->leftJoin('Customer.Zip Zip');
$q->addSelect('Customer.firstname as first_name');
$q->addSelect('Customer.postalcode as postalcode');
$q->setHydrationMode(Doctrine::HYDRATE_ARRAY);

Generates this DQL: 

SELECT Customer.firstname as first_name, Customer.postalcode as postalcode FROM Customer Customer LEFT JOIN Customer.Zip Zip

And this SQL:

SELECT c.firstname AS c_0, c.postalcode AS c_1 FROM customers c LEFT JOIN zips z ON c.postalcode = z.postalcode

Which results in this return after hyrdration: 

array('0'=>array('first_name'=>'Armando', 'postalcode'=>'00659'))

However the following code hydrates just fine: 

$q = Doctrine_Query::create();
$q->from('Customer Customer');
$q->addSelect('Customer.firstname as first_name');
$q->setHydrationMode(Doctrine::HYDRATE_ARRAY);

As does this code: 

$q = Doctrine_Query::create();
$q->from('Customer Customer');
$q->leftJoin('Customer.Zip Zip');
$q->addSelect('Customer.firstname');
$q->addSelect('Customer.postalcode as postalcode');
$q->setHydrationMode(Doctrine::HYDRATE_ARRAY);

Here is the yaml for the sample data I am testing on: 

detect_relations: false
package: Example
options:
type: INNODB
charset: utf8
Customer:
tableName: customers
columns:
customer_id:
type: integer(4)
primary: true
notnull: true
autoincrement: true
firstname:
type: string(45)
lastname:
type: string(45)
streetaddress:
type: string(45)
city:
type: string(45)
state:
type: string(45)
postalcode:
type: string(45)
relations:
Order:
type: many
local: customer_id
foreign: customer_id
Zip:
type: one
local: postalcode
foreign: postalcode
options:
type: InnoDB
Zip:
connection: default_schema
tableName: zips
columns:
postalcode:
type: varchar(30)
primary: true
latitude: 'float(10,6)'
longitude: 'float(10,6)'
city: string(50)
state: string(50)
country: string(50)
type: string(50)
relations:
Customer:
type: many
local: postalcode
foreign: postalcode

Perhaps there is something simple I am overlooking. To get around this I am just always selecting the primary key from my main table in every query.

Thanks in advance for any advice.
Will Ferrer