[plt-scheme] discrepancy in srfi-13

Hi all,

I am using srfi-13 and noticed that there is a discrepancy between
what the spec says and the implementation.

plt implementation says:
 string-delete char/char-set/pred string [start end]
 string-filter char/char-set/pred string [start end]

spec at srfi.schemers.org says:
 string-filter s char/char-set/pred [start end] -> string
 string-delete s char/char-set/pred [start end] -> string

Which one is portable to other schemes?

Regards,
Dima