diff --git a/src/core/timer.c b/src/core/timer.c
index 4e7fade999c..1527aab1582 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -263,7 +263,7 @@ static void timer_set_state(Timer *t, TimerState state) {
         unit_notify(UNIT(t), state_translation_table[old_state], state_translation_table[state], 0);
 }
 
-static void timer_enter_waiting(Timer *t, bool initial, bool time_change);
+static void timer_enter_waiting(Timer *t, bool time_change);
 
 static int timer_coldplug(Unit *u) {
         Timer *t = TIMER(u);
@@ -275,7 +275,7 @@ static int timer_coldplug(Unit *u) {
                 return 0;
 
         if (t->deserialized_state == TIMER_WAITING)
-                timer_enter_waiting(t, false, false);
+                timer_enter_waiting(t, false);
         else
                 timer_set_state(t, t->deserialized_state);
 
@@ -331,7 +331,7 @@ static void add_random(Timer *t, usec_t *v) {
         log_unit_debug(UNIT(t), "Adding %s random time.", format_timespan(s, sizeof(s), add, 0));
 }
 
-static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {
+static void timer_enter_waiting(Timer *t, bool time_change) {
         bool found_monotonic = false, found_realtime = false;
         bool leave_around = false;
         triple_timestamp ts;
@@ -441,7 +441,8 @@ static void timer_enter_waiting(Timer *t, bool initial, bool time_change) {
 
                         v->next_elapse = usec_add(usec_shift_clock(base, CLOCK_MONOTONIC, TIMER_MONOTONIC_CLOCK(t)), v->value);
 
-                        if (!initial && !time_change &&
+                        if (dual_timestamp_is_set(&t->last_trigger) &&
+                            !time_change &&
                             v->next_elapse < triple_timestamp_by_clock(&ts, TIMER_MONOTONIC_CLOCK(t)) &&
                             IN_SET(v->base, TIMER_ACTIVE, TIMER_BOOT, TIMER_STARTUP)) {
                                 /* This is a one time trigger, disable it now */
@@ -639,7 +640,7 @@ static int timer_start(Unit *u) {
         }
 
         t->result = TIMER_SUCCESS;
-        timer_enter_waiting(t, true, false);
+        timer_enter_waiting(t, false);
         return 1;
 }
 
@@ -754,14 +755,14 @@ static void timer_trigger_notify(Unit *u, Unit *other) {
         case TIMER_ELAPSED:
 
                 /* Recalculate sleep time */
-                timer_enter_waiting(t, false, false);
+                timer_enter_waiting(t, false);
                 break;
 
         case TIMER_RUNNING:
 
                 if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
                         log_unit_debug(UNIT(t), "Got notified about unit deactivation.");
-                        timer_enter_waiting(t, false, false);
+                        timer_enter_waiting(t, false);
                 }
                 break;
 
@@ -803,7 +804,7 @@ static void timer_time_change(Unit *u) {
                 t->last_trigger.realtime = ts;
 
         log_unit_debug(u, "Time change, recalculating next elapse.");
-        timer_enter_waiting(t, false, true);
+        timer_enter_waiting(t, true);
 }
 
 static void timer_timezone_change(Unit *u) {
@@ -815,7 +816,7 @@ static void timer_timezone_change(Unit *u) {
                 return;
 
         log_unit_debug(u, "Timezone change, recalculating next elapse.");
-        timer_enter_waiting(t, false, false);
+        timer_enter_waiting(t, false);
 }
 
 static const char* const timer_base_table[_TIMER_BASE_MAX] = {