diff --git a/changes/bug18816 b/changes/bug18816
new file mode 100644
index 0000000000..05455120c0
--- /dev/null
+++ b/changes/bug18816
@@ -0,0 +1,6 @@
+  o Minor bugfix (bootstrap):
+    - Consistently use the consensus download schedule for
+      authority certificates.
+    - When downloading authority certificates fails, switch from
+      using a fallback to using an authority.
+      Resolves ticket 18816; fix on fddb814fe in 0.2.4.13-alpha.
diff --git a/src/or/routerlist.c b/src/or/routerlist.c
index 1c275a68c3..31693437e1 100644
--- a/src/or/routerlist.c
+++ b/src/or/routerlist.c
@@ -148,6 +148,22 @@ get_n_authorities(dirinfo_type_t type)
   return n;
 }
 
+/** Initialise schedule, want_authority, and increment on in the download
+ * status dlstatus, then call download_status_reset() on it.
+ * It is safe to call this function or download_status_reset() multiple times
+ * on a new dlstatus. But it should *not* be called after a dlstatus has been
+ * used to count download attempts or failures. */
+static void
+download_status_cert_init(download_status_t *dlstatus)
+{
+  dlstatus->schedule = DL_SCHED_CONSENSUS;
+  dlstatus->want_authority = DL_WANT_ANY_DIRSERVER;
+  dlstatus->increment_on = DL_SCHED_INCREMENT_FAILURE;
+
+  /* Use the new schedule to set next_attempt_at */
+  download_status_reset(dlstatus);
+}
+
 /** Reset the download status of a specified element in a dsmap */
 static void
 download_status_reset_by_sk_in_cl(cert_list_t *cl, const char *digest)
@@ -168,6 +184,7 @@ download_status_reset_by_sk_in_cl(cert_list_t *cl, const char *digest)
     /* Insert before we reset */
     dlstatus = tor_malloc_zero(sizeof(*dlstatus));
     dsmap_set(cl->dl_status_map, digest, dlstatus);
+    download_status_cert_init(dlstatus);
   }
   tor_assert(dlstatus);
   /* Go ahead and reset it */
@@ -206,7 +223,7 @@ download_status_is_ready_by_sk_in_cl(cert_list_t *cl,
      * too.
      */
     dlstatus = tor_malloc_zero(sizeof(*dlstatus));
-    download_status_reset(dlstatus);
+    download_status_cert_init(dlstatus);
     dsmap_set(cl->dl_status_map, digest, dlstatus);
     rv = 1;
   }
@@ -225,7 +242,7 @@ get_cert_list(const char *id_digest)
   cl = digestmap_get(trusted_dir_certs, id_digest);
   if (!cl) {
     cl = tor_malloc_zero(sizeof(cert_list_t));
-    cl->dl_status_by_id.schedule = DL_SCHED_CONSENSUS;
+    download_status_cert_init(&cl->dl_status_by_id);
     cl->certs = smartlist_new();
     cl->dl_status_map = dsmap_new();
     digestmap_set(trusted_dir_certs, id_digest, cl);
@@ -895,11 +912,14 @@ authority_certs_fetch_missing(networkstatus_t *status, time_t now)
     } SMARTLIST_FOREACH_END(d);
 
     if (smartlist_len(fps) > 1) {
+      static int want_auth = 0;
       resource = smartlist_join_strings(fps, "", 0, NULL);
-      /* XXX - do we want certs from authorities or mirrors? - teor */
       directory_get_from_dirserver(DIR_PURPOSE_FETCH_CERTIFICATE, 0,
                                    resource, PDS_RETRY_IF_NO_SERVERS,
-                                   DL_WANT_ANY_DIRSERVER);
+                                   want_auth ? DL_WANT_AUTHORITY
+                                             : DL_WANT_ANY_DIRSERVER);
+      /* on failure, swap between using fallbacks and authorities */
+      want_auth = !want_auth;
       tor_free(resource);
     }
     /* else we didn't add any: they were all pending */
@@ -941,11 +961,14 @@ authority_certs_fetch_missing(networkstatus_t *status, time_t now)
     } SMARTLIST_FOREACH_END(d);
 
     if (smartlist_len(fp_pairs) > 1) {
+      static int want_auth = 0;
       resource = smartlist_join_strings(fp_pairs, "", 0, NULL);
-      /* XXX - do we want certs from authorities or mirrors? - teor */
       directory_get_from_dirserver(DIR_PURPOSE_FETCH_CERTIFICATE, 0,
                                    resource, PDS_RETRY_IF_NO_SERVERS,
-                                   DL_WANT_ANY_DIRSERVER);
+                                   want_auth ? DL_WANT_AUTHORITY
+                                             : DL_WANT_ANY_DIRSERVER);
+      /* on failure, swap between using fallbacks and authorities */
+      want_auth = !want_auth;
       tor_free(resource);
     }
     /* else they were all pending */