diff --git a/Customers/Invoices.aspx.vb b/Customers/Invoices.aspx.vb
index a435db0..ce6da6a 100644
--- a/Customers/Invoices.aspx.vb
+++ b/Customers/Invoices.aspx.vb
@@ -33,7 +33,7 @@ Partial Class Customers_Default3
             If Not csm1.IsStartupScriptRegistered(cstype, "Startup") Then
                 Dim string1 As String = "<script language=\""JavaScript\"">"
                 string1 += "</"
-                string1 += "window.addEventListener('beforeunload', (event) => {"
+                string1 += "window.addEventListener('onunload', (event) => {"
                 string1 += " event.preventDefault();"
                 string1 += "event.returnValue = '';"
                 string1 += "script>"