diff --git a/src/common/util.c b/src/common/util.c
index 99ac776dcb..6c6ce088ca 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -910,6 +910,10 @@ format_iso_time(char *buf, time_t t)
   strftime(buf, ISO_TIME_LEN+1, "%Y-%m-%d %H:%M:%S", tor_gmtime_r(&t, &tm));
 }
 
+/** Given an ISO-formatted UTC time value (after the epoch) in <b>cp</b>,
+ * parse it and store its value in *<b>t</b>.  Return 0 on success, -1 on
+ * failure.  Ignore extraneous stuff in <b>cp</b> separated by whitespace from
+ * the end of the time string. */
 int
 parse_iso_time(const char *cp, time_t *t)
 {
diff --git a/src/or/circuitbuild.c b/src/or/circuitbuild.c
index ed9ce5a762..6e36e1dabe 100644
--- a/src/or/circuitbuild.c
+++ b/src/or/circuitbuild.c
@@ -2275,6 +2275,7 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg)
         break;
     } else {
       time_t when;
+      time_t last_try = 0;
       if (!node) {
         *msg = tor_strdup("Unable to parse entry nodes: "
                "EntryGuardDownSince/UnlistedSince without EntryGuard");
@@ -2285,10 +2286,16 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg)
                           "Bad time in EntryGuardDownSince/UnlistedSince");
         break;
       }
-      if (!strcasecmp(line->key, "EntryGuardDownSince"))
+      if (strlen(line->value) >= ISO_TIME_LEN+ISO_TIME_LEN+1) {
+        /* ignore failure */
+        parse_iso_time(line->value+ISO_TIME_LEN+1, &last_try);
+      }
+      if (!strcasecmp(line->key, "EntryGuardDownSince")) {
         node->unreachable_since = when;
-      else
+        node->last_attempted = last_try;
+      } else {
         node->bad_since = when;
+      }
     }
   }
 
@@ -2348,8 +2355,12 @@ entry_guards_update_state(or_state_t *state)
       if (e->unreachable_since) {
         *next = line = tor_malloc_zero(sizeof(config_line_t));
         line->key = tor_strdup("EntryGuardDownSince");
-        line->value = tor_malloc(ISO_TIME_LEN+1);
+        line->value = tor_malloc(ISO_TIME_LEN+1+ISO_TIME_LEN+1);
         format_iso_time(line->value, e->unreachable_since);
+        if (e->last_attempted) {
+          line->value[ISO_TIME_LEN] = ' ';
+          format_iso_time(line->value+ISO_TIME_LEN+1, e->last_attempted);
+        }
         next = &(line->next);
       }
       if (e->bad_since) {