GetShipment: Key 'firstName' is missing in data array or is not a string

[DangerLifter]

Data returned by API call:

Array
(
    [shipmentId] => XXXXX
    [shipmentDate] => 2019-08-25T22:04:27+02:00
    [shipmentReference] => XXXX
    [shipmentItems] => Array
        (
            [0] => Array
                (
                    [orderItemId] => XXZ
                    [orderId] => XXX
                    [orderDate] => 2019-08-25T20:06:12+02:00
                    [latestDeliveryDate] => 2019-08-26
                    [ean] => XXXX
                    [title] => XXXXX
                    [quantity] => 1
                    [offerPrice] => 36.99
                    [offerCondition] => NEW
                    [offerReference] => XXXX
                    [fulfilmentMethod] => FBB
                )

        )

    [transport] => Array
        (
            [transportId] => XXX
            [transporterCode] => TNT
            [trackAndTrace] => XX
        )

    [customerDetails] => Array
        (
            [salutationCode] => XXX
            [zipCode] => XXX
            [countryCode] => NL
        )
)

In CustomerDetails.php line 207:

[InvalidArgumentException]
Key 'firstName' is missing in data array or is not a string

Exception trace: () at /var/www/projects/bol.com-app/vendor/bol-com/retailer-api/src/Model/Customer/CustomerDetails.php:207 BolCom\RetailerApi\Model\Customer\CustomerDetails::fromArray() at /var/www/projects/bol.com-app/vendor/bol-com/retailer-api/src/Model/Shipment/Shipment.php:157 BolCom\RetailerApi\Model\Shipment\Shipment::fromArray() at /var/www/projects/bol.com-app/vendor/bol-com/retailer-api/src/Handler/Shipment/GetShipmentHandler.php:46 BolCom\RetailerApi\Handler\Shipment\GetShipmentHandler->__invoke() at /var/www/projects/bol.com-app/vendor/bol-com/retailer-api/src/Infrastructure/MessageBus.php:111 BolCom\RetailerApi\Infrastructure\MessageBus->dispatch() at /var/www/projects/bol.com-app/src/Command/Local/BolComApiV3Command.php:53