Azure websites with .NET 4.5.2

问题:

According to this semi-official answer here, Azure websites now supports .NET 4.5.2:

https://stackoverflow.com/a/23554969/68231

However, when I visit the Kudu debug console, it doesn't show that .NET 4.5.2 is installed:

And indeed, when I try to push out a website targeted to .NET 4.5.2, Kudu refuses to build and deploy the website in question, with errors like this:

Areas\Integration\Controllers\TwitterController.cs(18,31): error CS0012: The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Runtime, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. [D:\home\site\repository\Payboard.Web\Payboard.Web.csproj]

What am I missing? Is there something I need to do to get 4.5.2 installed? Or...?