diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index 2329c128f..fc8e9d717 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -1324,7 +1324,7 @@ getword(const char * const s, SPICE_DSTRINGPTR tstr_p, const char **pi)
     iptr = *pi;
     const char *ls_ptr;
 
-    (ls_ptr - s) = (int) strlen(s);
+    ls_ptr = s + (int) strlen(s);
 
     do
         iptr++;