diff --git a/src/frontend/device.c b/src/frontend/device.c
index cbb7b0cc8..0e90f7ac9 100644
--- a/src/frontend/device.c
+++ b/src/frontend/device.c
@@ -1164,6 +1164,7 @@ com_alter_common(wordlist *wl, int do_model)
                 wl = wl->wl_next;
                 step = -1;
                 wl2 = wlin;
+                wl = NULL;
             } else if (strlen(argument) > 1) {
                 wl2 = wl_cons(copy_substring(argument, eqptr),
                               wl_cons(copy("="),