Angular complains that typescript module is not defined

I used Typewriter to convert my C# models to Typescript models. The template looks like this:

module Models { $Classes(*Model)[
    export class $Name { $Properties[
        $name: $Type;]
    }]
}

When I use this, I get this error:

Prerendering failed because of error: ReferenceError: Models is not defined

The Angular project is the default Visual Studio ASP.NET Core + Angular template