Using SSRS Data Feed as a source for Power BI

Hi,

I try to leverage a SSRS report as a data source to Power BI via the Data Feed / OData functionality. So I open the report, export it as a Data Feed, take the URL from the feed and try to use it as OData source in Power BI. I use Windows authentication. However I receive an error like: 

Details: "Microsoft.Mashup.Engine1.Library.Resources.HttpResource: Request failed: 
OData Version: 3 and 4, Error: The remote server returned an error: (500) Internal Server Error. (Server Error)
OData Version: 4, Error: The remote server returned an error: (500) Internal Server Error. (Server Error)
OData Version: 3, Error: The remote server returned an error: (500) Internal Server Error. (Server Error)"

Any idea? It's SQL 2016 (13.0.2149.0) with the newest build of Power BI (January 2018)

Thanks...