[NTG-context] pstopdf setting lower-case?

Hello, why is the ruby script pstopdf renaming files to lower-case? See the examples deukalion(pts/15)| ps2ps 1.ps U.ps deukalion(pts/15)| file U.ps U.ps: PostScript document text conforming DSC level 3.0, Level 2 deukalion(pts/15)| pstopdf U.ps PsToPdf | file U.ps does not exist deukalion(pts/15)| file U.ps U.ps: cannot open `U.ps' (No such file or directory) deukalion(pts/15)| cp 1.ps TEST.ps deukalion(pts/15)| file TEST.ps TEST.ps: PostScript document text conforming DSC level 3.0, type EPS, Level 1 deukalion(pts/15)| ls -lartsh TEST.ps 12K -rw-------. 1 pau pau 11K Nov 5 19:03 TEST.ps deukalion(pts/15)| pstopdf TEST.ps PsToPdf | file TEST.ps does not exist Thanks, Pau