Osmarender is black in PDF

[goldfndr]

When I open the PDF from http://walking-papers.org/print.php?id=h387f6s3 or http://walking-papers.org/print.php?id=h9nx38zh the content is black. Is there an issue with Osmarender and Walking Papers?
Also on someone else's: lz8nzm2g

[goldfndr]

Ah, I think I see the problem. When it says Zoom=16 on the web page, it'll be Zoom=18 on paper. It'd be great if the Zooming beyond 16 was disallowed to prevent this, or if there was a fallback exception for the Osmarender provider (perhaps have maxzoom for each provider?), or document that the Zoom on the web interface would result in +2 in the PDF.