diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index 8cd9ac59a..a8a25dd54 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -1003,15 +1003,15 @@ formula(dico_t *dico, const char *s, const char *s_end, bool *perror)
             fu = 0;
         } else if (alfa(c)) {
             const char *s_next = fetchid(s, s_end);
-            const char *t;
-            spice_dstring_reinit(&tstr);
-            for (t = s; t < s_next;)
-                cadd(&tstr, upcase(*t++));
             {
                 fu = keyword(fmathS, s, s_next); /* numeric function? */
                 if (fu > 0) {
                     state = S_init;  /* S_init means: ignore for the moment */
                 } else {
+                    const char *t;
+                    spice_dstring_reinit(&tstr);
+                    for (t = s; t < s_next;)
+                        cadd(&tstr, upcase(*t++));
                     u = fetchnumentry(dico, spice_dstring_value(&tstr), &error);
                     state = S_atom;
                 }