php - Can not join in a doctrine query

So I'm trying to do a join in a query but doctrine is doing its usually and throwing back errors that are as useful as a broken leg.

Can anyone advice on where I am going wrong here. The error message I am getting; debug: [Syntax Error] line 0, col -1: Error: Expected Doctrine\ORM\Query\Lexer::T_IDENTIFIER, got end of string. in file "./vendor/symfony/doctrine-bridge/Messenger/DoctrineTransactionMiddleware.php" on line 64

Assessment entity

 /**
 * @var Candidate
 * @ORM\ManyToOne(
 *          targetEntity="App\Domain\Candidate\Candidate",
 *          inversedBy="assessments")
 * @ORM\JoinColumn(nullable=false)
 */
private $candidate;
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Candidate entity

 /**
 * @var Assessment[]|Collection
 * @ORM\OneToMany(
 *      targetEntity="App\Domain\Assessment\Assessment",
 *      mappedBy="candidate",
 *      cascade={"persist"})
 * @ORM\JoinColumn(nullable=false)
 */
private $assessments;
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Doctrine query

$qb = $this->entityManager->createQueryBuilder();

$qb->select('ca')
    ->from(Candidate::class, 'ca')
    ->innerJoin('ca.assessments', 'as');
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