Swedish fintech firm Klarna will be the exclusive provider of buy now, pay later loans for Walmart, taking a coveted partnership away from rival Affirm, CNBC has learned.

BofA Securities analyst Jason Kupferberg said the decline in Affirm Holdings (AFRM) stock after a new Walmart/Klarna partnership is overdone, and Affirm should be able to manage any potential loss in business.

KEY TAKEAWAYS Affirm shares are tumbling Monday after rival Klarna, which is preparing to go public in the U.S., said it is now the exclusive provider of Buy Now, Pay Later loans for Walmart.Klarna said it would be partnering with OnePay to provide Walmart consumers with installment loans.