Comment by gchadwick

Surely the real bug is the reliance on the 'file' utility in the first place? It attempts to quickly identify a file that could be literaly anything so it's not surprising (and indeed should be expected) that sometimes it gets it wrong.

I don't know the details of the CUPS script but presumably it can only deal with a small number of different file types. Implementing it's own detection to positively identify PS vs whatever other formats it deals with vs everything else would be far more robust.