diff --git a/cfca/pkcs7_sign_test.go b/cfca/pkcs7_sign_test.go
index 728e840..4460d81 100644
--- a/cfca/pkcs7_sign_test.go
+++ b/cfca/pkcs7_sign_test.go
@@ -26,13 +26,12 @@ func TestSignMessageAttach(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	lastByte := p7[len(p7)-1]
-	p7[len(p7)-1] = 0
+	p7[0] = 0x20
 	err = VerifyMessageAttach(p7)
 	if err == nil {
 		t.Fatalf("VerifyMessageAttach() error = %v, wantErr %v", err, true)
 	}
-	p7[len(p7)-1] = lastByte
+	p7[0] = 0x30
 	err = VerifyMessageAttach(p7)
 	if err != nil {
 		t.Fatal(err)