filename parameter not working?

Tried to convert over URL while using filename parameter and while the pdf does get generated, it seems to just use some random filename like "1ggM72.pdf" and similar random characters 

Here's a sample link:
www.html2pdf.it/?filename=proposal&url=http://mydomain.com/proposalphp?q=2d0f80a2

I also tried to use other parameters like zoom and that seems to work. Could this be a bug? 