string-replace-substring is missing

[mbcladwell]

Hi,
Reading  
https://www.gnu.org/software/guile/manual/html_node/Miscellaneous-String-Operations.html
I learn that string-replace-substring is found in (ice-9 string-fun),  
but it is not:

(define-module (ice-9 string-fun)
  :export (split-after-char split-before-char split-discarding-char
           split-after-char-last split-before-char-last
           split-discarding-char-last split-before-predicate
           split-after-predicate split-discarding-predicate
           separate-fields-discarding-char separate-fields-after-char
           separate-fields-before-char string-prefix-predicate string-prefix=?
           sans-surrounding-whitespace sans-trailing-whitespace
           sans-leading-whitespace sans-final-newline has-trailing-newline?))
.....

Where do I find string-replace-substring?
Thanks
Mortimer