According to common opinion, the liability model underlying contractual liability for integrity damages is the fault model. This view holds that the debtor's promise to provide integrity protection to their contractual partner is only relevant for the distribution of the burden of proof. This common opinion questions the work and demonstrates that the debtor's promise has significance not only for the burden of proof but also for the underlying liability model. If the debtor promises integrity protection, they are subject to a guarantee liability. If they do not promise it, they are only liable for their own fault.