diff --git a/src/Dynamicweb.Ecommerce.CheckoutHandlers.QuickPayPaymentWindow.csproj b/src/Dynamicweb.Ecommerce.CheckoutHandlers.QuickPayPaymentWindow.csproj
index db1aa4f..0475c30 100644
--- a/src/Dynamicweb.Ecommerce.CheckoutHandlers.QuickPayPaymentWindow.csproj
+++ b/src/Dynamicweb.Ecommerce.CheckoutHandlers.QuickPayPaymentWindow.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
-		<VersionPrefix>10.1.2</VersionPrefix>
+		<VersionPrefix>10.1.3</VersionPrefix>
 		<AssemblyVersion>1.0.0.0</AssemblyVersion>
 		<Title>QuickPay Payment Window</Title>
 		<Description>The QuickPay Payment Window checkout handler is designed to work with QuickPay v10.</Description>
diff --git a/src/QuickPayPaymentWindow.cs b/src/QuickPayPaymentWindow.cs
index d84e335..96e972a 100644
--- a/src/QuickPayPaymentWindow.cs
+++ b/src/QuickPayPaymentWindow.cs
@@ -566,7 +566,7 @@ private void Callback(Order order)
     {
         lock (lockObject)
         {
-            if (Context.Current.Request.InputStream.Length == 0)
+            if (Converter.ToInt64(Context.Current.Request.Headers["Content-Length"]) == 0)
             {
                 LogEvent(order, "Invalid callback - no InputStream or not a POST");
                 return;