diff --git a/config/config.go b/config/config.go
index fdf6cf46fb..05cbf5fdd5 100644
--- a/config/config.go
+++ b/config/config.go
@@ -516,9 +516,13 @@ func checkTimeInterval(r *Route, timeIntervals map[string]struct{}) error {
 			return err
 		}
 	}
-	if len(r.MuteTimeIntervals) == 0 {
-		return nil
+
+	for _, mt := range r.ActiveTimeIntervals {
+		if _, ok := timeIntervals[mt]; !ok {
+			return fmt.Errorf("undefined time interval %q used in route", mt)
+		}
 	}
+
 	for _, mt := range r.MuteTimeIntervals {
 		if _, ok := timeIntervals[mt]; !ok {
 			return fmt.Errorf("undefined time interval %q used in route", mt)
diff --git a/config/config_test.go b/config/config_test.go
index 30a490700a..b0fca3e4cd 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -177,6 +177,32 @@ receivers:
 
 }
 
+func TestActiveTimeExists(t *testing.T) {
+	in := `
+route:
+    receiver: team-Y
+    routes:
+    -  match:
+        severity: critical
+       active_time_intervals:
+       - business_hours
+
+receivers:
+- name: 'team-Y'
+`
+	_, err := Load(in)
+
+	expected := "undefined time interval \"business_hours\" used in route"
+
+	if err == nil {
+		t.Fatalf("no error returned, expected:\n%q", expected)
+	}
+	if err.Error() != expected {
+		t.Errorf("\nexpected:\n%q\ngot:\n%q", expected, err.Error())
+	}
+
+}
+
 func TestMuteTimeHasName(t *testing.T) {
 	in := `
 mute_time_intervals:
diff --git a/notify/notify_test.go b/notify/notify_test.go
index b120fd670d..808f7a4f9e 100644
--- a/notify/notify_test.go
+++ b/notify/notify_test.go
@@ -724,7 +724,8 @@ func TestMuteStageWithSilences(t *testing.T) {
 }
 
 func TestTimeMuteStage(t *testing.T) {
-	// Route mutes alerts outside business hours.
+	// Route mutes alerts outside business hours if it is a mute_time_interval
+	// Route mutes alerts inside business hours if it is an active time interval
 	muteIn := `
 ---
 - weekdays: ['monday:friday']
@@ -736,45 +737,80 @@ func TestTimeMuteStage(t *testing.T) {
 - weekdays: ['saturday', 'sunday']`
 
 	cases := []struct {
-		fireTime   string
-		labels     model.LabelSet
-		shouldMute bool
+		fireTime      string
+		labels        model.LabelSet
+		setupAsActive bool
+		shouldMute    bool
 	}{
+		//{
+		//	// Friday during business hours
+		//	fireTime:      "01 Jan 21 09:00 +0000",
+		//	labels:        model.LabelSet{"foo": "bar"},
+		//	setupAsActive: false,
+		//	shouldMute:    false,
+		//},
+		//{
+		//	// Tuesday before 5pm
+		//	fireTime:      "01 Dec 20 16:59 +0000",
+		//	labels:        model.LabelSet{"dont": "mute"},
+		//	setupAsActive: false,
+		//	shouldMute:    false,
+		//},
+		//{
+		//	// Saturday
+		//	fireTime:      "17 Oct 20 10:00 +0000",
+		//	labels:        model.LabelSet{"mute": "me"},
+		//	setupAsActive: false,
+		//	shouldMute:    true,
+		//},
+		//{
+		//	// Wednesday before 9am
+		//	fireTime:      "14 Oct 20 05:00 +0000",
+		//	labels:        model.LabelSet{"mute": "me"},
+		//	setupAsActive: false,
+		//	shouldMute:    true,
+		//},
+		//{
+		//	// Ensure comparisons are UTC only. 12:00 KST should be muted (03:00 UTC)
+		//	fireTime:      "14 Oct 20 12:00 +0900",
+		//	labels:        model.LabelSet{"mute": "kst"},
+		//	setupAsActive: false,
+		//	shouldMute:    true,
+		//},
+		//{
+		//	// Ensure comparisons are UTC only. 22:00 KST should not be muted (13:00 UTC)
+		//	fireTime:      "14 Oct 20 22:00 +0900",
+		//	labels:        model.LabelSet{"kst": "dont_mute"},
+		//	setupAsActive: false,
+		//	shouldMute:    false,
+		//},
 		{
 			// Friday during business hours
-			fireTime:   "01 Jan 21 09:00 +0000",
-			labels:     model.LabelSet{"foo": "bar"},
-			shouldMute: false,
+			fireTime:      "01 Jan 21 09:00 +0000",
+			labels:        model.LabelSet{"mute": "me"},
+			setupAsActive: true,
+			shouldMute:    true,
 		},
 		{
 			// Tuesday before 5pm
-			fireTime:   "01 Dec 20 16:59 +0000",
-			labels:     model.LabelSet{"dont": "mute"},
-			shouldMute: false,
+			fireTime:      "01 Dec 20 16:59 +0000",
+			labels:        model.LabelSet{"mute": "me"},
+			setupAsActive: true,
+			shouldMute:    true,
 		},
 		{
 			// Saturday
-			fireTime:   "17 Oct 20 10:00 +0000",
-			labels:     model.LabelSet{"mute": "me"},
-			shouldMute: true,
+			fireTime:      "17 Oct 20 10:00 +0000",
+			labels:        model.LabelSet{"foo": "bar"},
+			setupAsActive: true,
+			shouldMute:    false,
 		},
 		{
 			// Wednesday before 9am
-			fireTime:   "14 Oct 20 05:00 +0000",
-			labels:     model.LabelSet{"mute": "me"},
-			shouldMute: true,
-		},
-		{
-			// Ensure comparisons are UTC only. 12:00 KST should be muted (03:00 UTC)
-			fireTime:   "14 Oct 20 12:00 +0900",
-			labels:     model.LabelSet{"mute": "kst"},
-			shouldMute: true,
-		},
-		{
-			// Ensure comparisons are UTC only. 22:00 KST should not be muted (13:00 UTC)
-			fireTime:   "14 Oct 20 22:00 +0900",
-			labels:     model.LabelSet{"kst": "dont_mute"},
-			shouldMute: false,
+			fireTime:      "14 Oct 20 05:00 +0000",
+			labels:        model.LabelSet{"dont": "mute"},
+			setupAsActive: true,
+			shouldMute:    false,
 		},
 	}
 	var intervals []timeinterval.TimeInterval
@@ -800,7 +836,13 @@ func TestTimeMuteStage(t *testing.T) {
 		alerts := []*types.Alert{{Alert: a}}
 		ctx := context.Background()
 		ctx = WithNow(ctx, now)
-		ctx = WithMuteTimeIntervals(ctx, []string{"test"})
+		if tc.setupAsActive {
+			ctx = WithActiveTimeIntervals(ctx, []string{"test"})
+			ctx = WithMuteTimeIntervals(ctx, []string{})
+		} else {
+			ctx = WithActiveTimeIntervals(ctx, []string{})
+			ctx = WithMuteTimeIntervals(ctx, []string{"test"})
+		}
 
 		_, out, err := stage.Exec(ctx, log.NewNopLogger(), alerts...)
 		if err != nil {