diff --git a/GUIs.Test.ZUGFeRDTest/Form1.vb b/GUIs.Test.ZUGFeRDTest/Form1.vb
index 18853c48..16870629 100644
--- a/GUIs.Test.ZUGFeRDTest/Form1.vb
+++ b/GUIs.Test.ZUGFeRDTest/Form1.vb
@@ -117,6 +117,7 @@ Public Class Form1
 
     Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
         ListBox1.Text = ""
+        ListBox1.Items.Clear()
         Dim oDialogResult = OpenFileDialog1.ShowDialog()
         Dim oArgs As New WorkerArgs() With {
             .AllowFacturX = False,