Indic fonts do not render properly when exporting PPTX in headless mode

I am exporting a PPTX file to PNG in LibreOffice on Ubuntu 13.04 x64

The problem is that when exporting in headless mode, the Telugu / Hindi fonts do not render correctly on the PNG. However, if I open the PPTX in the GUI and export a single slide to PNG, then the slide appears correctly. This tells me that there is no problem of the correct fonts being installed.

I suspect this is a bug, but I’m not sure, so I wanted to ask for assistance first. I replicate the same behavior on my ubuntu desktop and also when exporting on an Ubuntu server without Xserver installed, but with the ttf-indic-fonts package installed.

In order to see the incorrectly rendered slides, try something like:
unoconv -f html Telugu.pptx

Where Telegu.pptx can be downloaded from here:

Can anyone tell me how to make the export behave correctly in headless mode?