diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index 6325dca54..abd0bbee9 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -1321,8 +1321,10 @@ getword(const char *s, const char * const s_end, SPICE_DSTRINGPTR tstr_p)
 /* isolate a word from s after position "after". return i= last read+1 */
 {
     s++;
-    while ((s-1 < s_end - 1) && !alfa(s[-1]))
+    s--;
+    while ((s < s_end - 1) && !alfa(*s))
         s++;
+    s++;
 
     spice_dstring_reinit(tstr_p);