Comment 4 for bug 278113

Addendum: Audio and some text icons don't seem affected by this. audio-mpeg, audio-x-wav, audio-x-ms-wma, text-x-csrc, text-x-c++src, text-x-chdr show up correctly.

In general, mimetypes that have the generic-icon element set in the MIME database (/usr/share/mime/packages) always use the generic icon, instead of using it only if there is no specific icon in the current theme.