SwissQRBill: QR bill data is invalid: reference is invalid

I’m using your great library to generate QR code only for my QR-bill in PNG and I get an exception when generating the QR code:

net.codecrete.qrbill.generator.QRBillValidationError: QR bill data is invalid: reference is invalid (reference should be empty or start with “RF”) (valid_iso11649_creditor_ref)

I generate the reference number using Payments.createQRReference() and it’s formatted with Payments.formatQRReferenceNumber(). The generated string is a valid QR référence according to the standard.

00 00000 00000 00000 00000 00034