diff --git a/sign/sign.go b/sign/sign.go
index 266d9fd..a81aa3e 100644
--- a/sign/sign.go
+++ b/sign/sign.go
@@ -56,7 +56,7 @@ type SignDataSignature struct {
 }
 
 const (
-	ApprovalSignature = iota + 1
+	ApprovalSignature = iota
 	CertificationSignature
 	UsageRightsSignature
 )