diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index e8708ef9ef..0cc100a6e6 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -2093,6 +2093,7 @@ networkstatus_parse_vote_from_string(const char *s, const char **eos_out,
   struct in_addr in;
   int i, inorder, n_signatures = 0;
   memarea_t *area = NULL, *rs_area = NULL;
+  tor_assert(s);
 
   if (router_get_networkstatus_v3_hash(s, ns_digest)) {
     log_warn(LD_DIR, "Unable to compute digest of network-status");