diff --git a/src/core/timer.c b/src/core/timer.c
index 419416b3255..aab376e5cc7 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -399,14 +399,12 @@ static void timer_enter_waiting(Timer *t, bool time_change) {
                          * to that. If we don't, just start from
                          * the activation time. */
 
-                        if (t->last_trigger.realtime > 0)
+                        if (dual_timestamp_is_set(&t->last_trigger))
                                 b = t->last_trigger.realtime;
-                        else {
-                                if (state_translation_table[t->state] == UNIT_ACTIVE)
-                                        b = UNIT(t)->inactive_exit_timestamp.realtime;
-                                else
-                                        b = ts.realtime;
-                        }
+                        else if (dual_timestamp_is_set(&UNIT(t)->inactive_exit_timestamp))
+                                b = UNIT(t)->inactive_exit_timestamp.realtime;
+                        else
+                                b = ts.realtime;
 
                         r = calendar_spec_next_usec(v->calendar_spec, b, &v->next_elapse);
                         if (r < 0)