diff --git a/src/frontend/numparam/spicenum.c b/src/frontend/numparam/spicenum.c
index 42c2c3e6d..00399ee47 100644
--- a/src/frontend/numparam/spicenum.c
+++ b/src/frontend/numparam/spicenum.c
@@ -702,10 +702,10 @@ nupa_copy(struct card *deck)
     spice_dstring_init(&u);
     s_end = s + (int) strlen(s);
 
-    while ((s_end - s > 0) && (s[s_end - s - 1] <= ' '))
+    while (s_end > s && s_end[-1] <= ' ')
         s_end--;
 
-    pscopy(&u, s, s + (s_end - s));       /* strip trailing space, CrLf and so on */
+    pscopy(&u, s, s_end);       /* strip trailing space, CrLf and so on */
     dicoS->srcline = linenum;
 
     if ((!inexpansionS) && (linenum >= 0) && (linenum <= dynmaxline)) {