// key usages.
			return candidateChains, nil
		}
	}

	chains = make([][]*Certificate, 0, len(candidateChains))
	for _, candidate := range candidateChains {
		if checkChainForKeyUsage(candidate, opts.KeyUsages) {
			chains = append(chains, candidate)
		}
	}

	if len(chains) == 0 {
		return nil, CertificateInvalidError{c, IncompatibleUsage, ""}
	}

	return chains, nil
}