diff --git a/verify.go b/verify.go
index 4fdef78..e1fed88 100644
--- a/verify.go
+++ b/verify.go
@@ -350,6 +350,14 @@ func getCertFromCertsByIssuerAndSerial(certs []*x509.Certificate, ias issuerAndS
 	return nil
 }
 
+type AttributeNotFoundError struct {
+	AttributeType asn1.ObjectIdentifier
+}
+
+func (a AttributeNotFoundError) Error() string {
+	return fmt.Sprintf("pkcs7: attribute %s does not exist", a.AttributeType)
+}
+
 func unmarshalAttribute(attrs []attribute, attributeType asn1.ObjectIdentifier, out interface{}) error {
 	for _, attr := range attrs {
 		if attr.Type.Equal(attributeType) {
@@ -357,5 +365,5 @@ func unmarshalAttribute(attrs []attribute, attributeType asn1.ObjectIdentifier,
 			return err
 		}
 	}
-	return errors.New("pkcs7: attribute type not in attributes")
+	return AttributeNotFoundError{AttributeType: attributeType}
 }