Spot the bug in the invoice controller

@RestController
class InvoiceController {
    private final InvoiceRepository invoices;

    @GetMapping("/accounts/{accountId}/invoices/{invoiceId}")
    Invoice invoice(@PathVariable long accountId, @PathVariable long invoiceId) {
        return invoices.findById(invoiceId)
                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND));
    }
}