diff --git a/src/frontend/device.c b/src/frontend/device.c
index a3087fabc..dbf39ffe7 100644
--- a/src/frontend/device.c
+++ b/src/frontend/device.c
@@ -1343,10 +1343,15 @@ com_alter_common(wordlist *wl, int do_model)
     dev = NULL;
     param = NULL;
     words = wl;
-    while (words != eqword) {
+    while (words && words != eqword) {
         char *p = words->wl_word;
         if (param) {
             fprintf(cp_err, "Warning: excess parameter name \"%s\" ignored.\n", p);
+            char* line = wl_flatten(wl_head->wl_prev);
+            if (line) {
+                fprintf(cp_err, "    in line: %s\n", line);
+                tfree(line);
+            }
         } else if (dev) {
             param = words->wl_word;
         } else if (*p == '@' || *p == '#') {