diff --git a/include/SWI-Prolog.h b/include/SWI-Prolog.h
index 54e2b7bd0..40afe2330 100755
--- a/include/SWI-Prolog.h
+++ b/include/SWI-Prolog.h
@@ -372,7 +372,7 @@ extern X_API int PL_get_arg(int, term_t, term_t);
 extern X_API int _PL_get_arg(int, term_t, term_t);
 extern X_API int PL_get_atom(term_t, atom_t *);
 extern X_API int PL_get_atom_chars(term_t, char **);
-extern X_API int PL_get_atom_nchars(term_t, char **, size_t *);
+extern X_API int PL_get_atom_nchars(term_t, size_t *, char **);
 extern X_API int PL_get_bool(term_t, int *);
 extern X_API int PL_get_chars(term_t, char **, unsigned);
 extern X_API int PL_get_nchars(term_t, size_t *, char **, unsigned);
diff --git a/library/yap2swi/yap2swi.c b/library/yap2swi/yap2swi.c
index 614aaafad..d2368863d 100755
--- a/library/yap2swi/yap2swi.c
+++ b/library/yap2swi/yap2swi.c
@@ -393,7 +393,7 @@ X_API int PL_get_atom_chars(term_t ts, char **a)  /* SAM check type */
 
 /* SWI: int PL_get_atom_chars(term_t t, char **s)
    YAP: char* AtomName(Atom) */
-X_API int PL_get_atom_nchars(term_t ts, char **s, size_t *len)  /* SAM check type */
+X_API int PL_get_atom_nchars(term_t ts, size_t *len, char **s)  /* SAM check type */
 {
   Term t = Yap_GetFromSlot(ts);
   if (!IsAtomTerm(t))