diff --git a/acme/client.go b/acme/client.go
index 6897ed4b..ae67b897 100644
--- a/acme/client.go
+++ b/acme/client.go
@@ -232,6 +232,8 @@ func (c *Client) ObtainCertificates(domains []string, bundle bool) ([]Certificat
 // domains are added using the Subject Alternate Names extension.
 // If bundle is true, the []byte contains both the issuer certificate and
 // your issued certificate as a bundle.
+// This function will never return a partial certificate. If one domain in the list fails,
+// the while certificate will fail.
 func (c *Client) ObtainSANCertificate(domains []string, bundle bool) (CertificateResource, map[string]error) {
 	if bundle {
 		logf("[INFO] acme: Obtaining bundled SAN certificate for %v", strings.Join(domains, ", "))