Script Combining issue with Version 8.0.5710.0

Hi,
I have been trying to combine script in Sitefinity Version 8.0.5710.0, but could not do it.
I followed the following steps to combine the scripts.

Step-1
I added the telerik:RadScriptManager  under the form tag in my main.master file   
<form id="form1" runat="server">
        <telerik:RadScriptManager ID="RadScriptManager1" runat="server" EnableScriptCombine="true">
            <Scripts>
                <telerik:RadScriptReference Path="/assets/js/jquery.min.js" />
                <telerik:RadScriptReference Path="/assets/js/jquery-ui.min.js" />

            </Scripts>
        </telerik:RadScriptManager>

Step-2
Add the following keys in the web.config file.
  <appSettings>   
    <add key="Telerik.Web.UI.ScriptsFolder" value="~/ assets /js/;"/>
</appSettings>

Step-3
Following handler entry already added the httpHandler section of   <system.web>  <httpHandlers><add verb="*" path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" validate="false"/> </httpHandlers>

I followed the same steps in Sitefinity Version 8.2.5900 and its working perfectly.
Can anyone guide me is there any specific settings for combining the script with radScriptManager.

Regards,
Mubashir