slib and print-call-stack

Hi all,
in the slib.scm provided with SISC the procedure print-call-stack seems 
to be undefined:

#;> (require-library 'sisc/libs/slib)
(sisc/libs/slib (sisc/libs/srfi/srfi-59))
#;> (slib:warn "sdsds")
Error: undefined variable 'print-call-stack'.

Thanks
Bye

-- 
Cesare

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