diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index 2eb03b611..b0d69e54a 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -1655,13 +1655,14 @@ nupa_subcktcall(dico_t *dico, char *s, char * const x, char * const inst_name)
 
                 char * const u_p = spice_dstring_value(&ustr);
                 if (u_p[0]) {
-                    char *dollar = strchr(spice_dstring_value(&idlist), '$');
+                    char * const idlist_p = spice_dstring_value(&idlist);
+                    char *dollar = strchr(idlist_p, '$');
                     if (dollar) {
-                        int kk = (int) (dollar - spice_dstring_value(&idlist));
+                        int kk = (int) (dollar - idlist_p);
                         /* replace dollar with expression string u */
-                        pscopy(&vstr, spice_dstring_value(&idlist), 0, kk);
+                        pscopy(&vstr, idlist_p, 0, kk);
                         sadd(&vstr, spice_dstring_value(&ustr));
-                        sadd(&vstr, spice_dstring_value(&idlist) + kk + 1);
+                        sadd(&vstr, idlist_p + kk + 1);
                         scopyd(&idlist, &vstr);
                     }
                     narg++;