diff --git a/mailreply00.go b/mailreply00.go
index 9623c26..45a331a 100644
--- a/mailreply00.go
+++ b/mailreply00.go
@@ -18,13 +18,13 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/mholt/acmez/acme"
+	"github.com/mholt/acmez/v2/acme"
 )
 
-// MailReplyChallengeResponse builds an email response body including headers to reply to the 
+// MailReplyChallengeResponse builds an email response body including headers to reply to the
 // email-reply-00 challenge email. This function only builds the email body; sending the
-// message has to be performed by the caller of this function. The mailSubject and 
-// messageId come from the challenge mail, and if there is no reply-to header in the 
+// message has to be performed by the caller of this function. The mailSubject and
+// messageId come from the challenge mail, and if there is no reply-to header in the
 // challenge email, the replyTo parameter should be empty.
 func MailReplyChallengeResponse(c acme.Challenge, mailSubject string, messageId string, replyTo string) string {
 	if len(replyTo) == 0 {