WebForms.js not minified

I'm using the script manager in the master page of my website:

<asp:ScriptManager ID="myScriptManager" EnableCdn="true" runat="server"></asp:ScriptManager>

It outputs in the html the inclusion of some javascripts files all minified except this one:

<script src="https://ajax.aspnetcdn.com/ajax/4.5.1/1/WebForms.js" type="text/javascript"></script>

How can I get the minified version for WebForms.js?

Thanks