diff --git a/doc/chibi.scrbl b/doc/chibi.scrbl
index 3015aad0..4507bea5 100755
--- a/doc/chibi.scrbl
+++ b/doc/chibi.scrbl
@@ -689,8 +689,8 @@ Scheme strings are length bounded C strings which can be accessed with
 the following macros:
 
 \itemlist[
-\item{\ccode{char* sexp_string_data(s)} - the raw bytes of the string}
-\item{\ccode{sexp_uint_t sexp_string_size(s)} - the number of raw bytes in the string}
+\item{\ccode{char* sexp_string_data(sexp s)} - the raw bytes of the string}
+\item{\ccode{sexp_uint_t sexp_string_size(sexp s)} - the number of raw bytes in the string}
 \item{\ccode{sexp_uint_t sexp_string_length(sexp s)} - the number of characters encoded in \var{s}}
 ]