In the case referred to in 4° of III of article L. 214-165-1, either the issuing company, or a company in the same group within the meaning of I of the same article, undertakes to redeem these securities at the first request of the subscriber at their nominal value plus accrued interest, or an equivalent mechanism is set up to guarantee their redemption on the same terms. In addition, when these debt securities are included in the assets of a fund covered by this paragraph, the valuation method is defined by an independent expert when the fund subscribes to these securities and each time an event or series of subsequent events is likely to lead to a substantial change in the risk of default by the company.