diff --git a/dispatch/dispatch.go b/dispatch/dispatch.go
index 4ae5c28568..b737a0d252 100644
--- a/dispatch/dispatch.go
+++ b/dispatch/dispatch.go
@@ -450,7 +450,7 @@ func (ag *aggrGroup) run(nf notifyFunc) {
 
 			// Wait the configured interval before calling flush again.
 			ag.mtx.Lock()
-			ag.next.Reset(ag.opts.GroupWait)
+			ag.next.Reset(ag.opts.GroupInterval)
 			ag.hasFlushed = true
 			ag.mtx.Unlock()
 
diff --git a/notify/notify.go b/notify/notify.go
index e9ca40fbf2..a3f989bbfd 100644
--- a/notify/notify.go
+++ b/notify/notify.go
@@ -573,14 +573,15 @@ func hashAlert(a *types.Alert) uint64 {
 	return hash
 }
 
-func (n *DedupStage) needsUpdate(entry *nflogpb.Entry, firing, resolved map[uint64]struct{}, repeat, groupInterval time.Duration) bool {
+func (n *DedupStage) needsUpdate(entry *nflogpb.Entry, firing, resolved map[uint64]struct{}, repeat, groupInterval time.Duration, now time.Time) bool {
 	// If we haven't notified about the alert group before, notify right away
 	// unless we only have resolved alerts.
 	if entry == nil {
 		return len(firing) > 0
 	}
 
-	groupIntervalMuted := len(entry.FiringAlerts) > 0 && entry.Timestamp.After(time.Now().Add(-groupInterval))
+	groupIntervalExpired := float64(now.UnixMilli()-entry.Timestamp.UnixMilli())/float64(groupInterval.Milliseconds()) >= 0.99
+	groupIntervalMuted := len(entry.FiringAlerts) > 0 && !groupIntervalExpired
 
 	if !entry.IsFiringSubset(firing) && !groupIntervalMuted {
 		return true
@@ -589,7 +590,7 @@ func (n *DedupStage) needsUpdate(entry *nflogpb.Entry, firing, resolved map[uint
 	// Notify about all alerts being resolved.
 	// This is done irrespective of the send_resolved flag to make sure that
 	// the firing alerts are cleared from the notification log.
-	if len(firing) == 0 {
+	if len(firing) == 0 && !groupIntervalMuted {
 		// If the current alert group and last notification contain no firing
 		// alert, it means that some alerts have been fired and resolved during the
 		// last interval. In this case, there is no need to notify the receiver
@@ -597,7 +598,7 @@ func (n *DedupStage) needsUpdate(entry *nflogpb.Entry, firing, resolved map[uint
 		return len(entry.FiringAlerts) > 0
 	}
 
-	if n.rs.SendResolved() && !groupIntervalMuted {
+	if n.rs.SendResolved() && !entry.IsResolvedSubset(resolved) && !groupIntervalMuted {
 		return true
 	}
 
@@ -622,6 +623,11 @@ func (n *DedupStage) Exec(ctx context.Context, _ log.Logger, alerts ...*types.Al
 		return ctx, nil, errors.New("repeat interval missing")
 	}
 
+	now, ok := Now(ctx)
+	if !ok {
+		return ctx, nil, errors.New("now timestamp missing")
+	}
+
 	firingSet := map[uint64]struct{}{}
 	resolvedSet := map[uint64]struct{}{}
 	firing := []uint64{}
@@ -656,9 +662,10 @@ func (n *DedupStage) Exec(ctx context.Context, _ log.Logger, alerts ...*types.Al
 		return ctx, nil, errors.Errorf("unexpected entry result size %d", len(entries))
 	}
 
-	if n.needsUpdate(entry, firingSet, resolvedSet, repeatInterval, groupInterval) {
+	if n.needsUpdate(entry, firingSet, resolvedSet, repeatInterval, groupInterval, now) {
 		return ctx, alerts, nil
 	}
+
 	return ctx, nil, nil
 }
 
diff --git a/notify/notify_test.go b/notify/notify_test.go
index 50aef9a35a..a5da56df31 100644
--- a/notify/notify_test.go
+++ b/notify/notify_test.go
@@ -207,7 +207,7 @@ func TestDedupStageNeedsUpdate(t *testing.T) {
 			now: func() time.Time { return now },
 			rs:  sendResolved(c.resolve),
 		}
-		res := s.needsUpdate(c.entry, c.firingAlerts, c.resolvedAlerts, c.repeat, 2*time.Hour)
+		res := s.needsUpdate(c.entry, c.firingAlerts, c.resolvedAlerts, c.repeat, 2*time.Hour, now)
 		require.Equal(t, c.res, res)
 	}
 }
@@ -234,6 +234,12 @@ func TestDedupStage(t *testing.T) {
 
 	ctx = WithGroupKey(ctx, "1")
 
+	_, _, err = s.Exec(ctx, log.NewNopLogger())
+	require.EqualError(t, err, "group interval missing")
+
+	ctx = WithGroupKey(ctx, "1")
+	ctx = WithGroupInterval(ctx, time.Hour)
+
 	_, _, err = s.Exec(ctx, log.NewNopLogger())
 	require.EqualError(t, err, "repeat interval missing")
 
@@ -288,7 +294,7 @@ func TestDedupStage(t *testing.T) {
 		qres: []*nflogpb.Entry{
 			{
 				FiringAlerts: []uint64{1, 2, 3, 4},
-				Timestamp:    now,
+				Timestamp:    now.Add(-time.Hour),
 			},
 		},
 	}
diff --git a/test/with_api_v2/acceptance/send_test.go b/test/with_api_v2/acceptance/send_test.go
index 4e13d37ca5..b507229b1b 100644
--- a/test/with_api_v2/acceptance/send_test.go
+++ b/test/with_api_v2/acceptance/send_test.go
@@ -207,9 +207,9 @@ receivers:
 	am.Push(At(1), Alert("alertname", "test1"))
 
 	co1.Want(Between(2, 2.5), Alert("alertname", "test1").Active(1))
-	co1.Want(Between(6, 6.5), Alert("alertname", "test1").Active(1))
+	co1.Want(Between(5, 6.5), Alert("alertname", "test1").Active(1))
 
-	co2.Want(Between(6, 6.5), Alert("alertname", "test1").Active(1))
+	co2.Want(Between(5, 6.5), Alert("alertname", "test1").Active(1))
 
 	at.Run()