diff --git a/GUIs.Test.ZUGFeRDTest/Form1.vb b/GUIs.Test.ZUGFeRDTest/Form1.vb
index 23c94dd0..40cea31b 100644
--- a/GUIs.Test.ZUGFeRDTest/Form1.vb
+++ b/GUIs.Test.ZUGFeRDTest/Form1.vb
@@ -129,6 +129,7 @@ Public Class Form1
         If oDialogResult = DialogResult.OK Then
             Dim oDoc = _zugferd.ValidateZUGFeRDFileWithGDPicture(OpenFileDialog1.FileName)
             Dim oResult = _zugferd.SerializeZUGFeRDDocument(oDoc)
+            oResult = _zugferd.ValidateZUGFeRDDocument(oResult)
 
             WriteLog("Specification: " & oResult.Specification)
             WriteLog("Embedded File Name: " & oResult.DataFileName)