diff --git a/web/documentserver-example/csharp-mvc/Scripts/jscript.js b/web/documentserver-example/csharp-mvc/Scripts/jscript.js
index ca5a789d..683fff92 100644
--- a/web/documentserver-example/csharp-mvc/Scripts/jscript.js
+++ b/web/documentserver-example/csharp-mvc/Scripts/jscript.js
@@ -122,7 +122,7 @@ if (typeof jQuery != "undefined") {
 
         var fileName = jq("#hiddenFileName").val();
         var posExt = fileName.lastIndexOf('.');
-        posExt = 0 <= posExt ? fileName.substring(posExt).trim().toLowerCase() : '';
+        posExt = 0 <= posExt ? fileName.substring(posExt + 1).trim().toLowerCase() : '';
 
         if (!formatManager.isAutoConvertible(posExt)) {
             jq("#step2").addClass("done").removeClass("current");