Error with recurring payment

Problem/Motivation

When using recurrent payment on payment method redsys, the proccess is giving this error on payment:

CommerceRedsys\Payment\SermepaException: Must enter a valid Ds_Merchant_DateFrecuency. in CommerceRedsys\Payment\Sermepa->check() (line 372 of /var/www/html/vendor/commerceredsys/sermepa/src/Sermepa.php).

Steps to reproduce

Add payment method with redsys and configure transaction type as Recurring transaction.
After this try to buy a product with this payment type.