diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index f6619cb902..8170bbb057 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -3697,6 +3697,7 @@ router_parse_addr_policy_item_from_string,(const char *s, int assume_action,
   memarea_t *area = NULL;
 
   tor_assert(malformed_list);
+  *malformed_list = 0;
 
   s = eat_whitespace(s);
   if ((*s == '*' || TOR_ISDIGIT(*s)) && assume_action >= 0) {