diff --git a/app/vmalert/manager.go b/app/vmalert/manager.go
index 3ab70c6f40..5fc2586429 100644
--- a/app/vmalert/manager.go
+++ b/app/vmalert/manager.go
@@ -172,6 +172,7 @@ func (g *Group) toAPI() APIGroup {
 		Params:         urlValuesToStrings(g.Params),
 		Labels:         g.Labels,
 	}
+	ag.Rules = make([]APIRule, 0)
 	for _, r := range g.Rules {
 		ag.Rules = append(ag.Rules, r.ToAPI())
 	}
diff --git a/app/vmalert/web_test.go b/app/vmalert/web_test.go
index bc84f64d99..97ae209981 100644
--- a/app/vmalert/web_test.go
+++ b/app/vmalert/web_test.go
@@ -130,8 +130,8 @@ func TestHandler(t *testing.T) {
 }
 
 func TestEmptyResponse(t *testing.T) {
-	rh := &requestHandler{m: &manager{groups: make(map[uint64]*Group)}}
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { rh.handler(w, r) }))
+	rhWithNoGroups := &requestHandler{m: &manager{groups: make(map[uint64]*Group)}}
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { rhWithNoGroups.handler(w, r) }))
 	defer ts.Close()
 
 	getResp := func(url string, to interface{}, code int) {
@@ -155,7 +155,7 @@ func TestEmptyResponse(t *testing.T) {
 		}
 	}
 
-	t.Run("/api/v1/alerts", func(t *testing.T) {
+	t.Run("no groups /api/v1/alerts", func(t *testing.T) {
 		lr := listAlertsResponse{}
 		getResp(ts.URL+"/api/v1/alerts", &lr, 200)
 		if lr.Data.Alerts == nil {
@@ -169,7 +169,7 @@ func TestEmptyResponse(t *testing.T) {
 		}
 	})
 
-	t.Run("/api/v1/rules", func(t *testing.T) {
+	t.Run("no groups /api/v1/rules", func(t *testing.T) {
 		lr := listGroupsResponse{}
 		getResp(ts.URL+"/api/v1/rules", &lr, 200)
 		if lr.Data.Groups == nil {
@@ -182,4 +182,26 @@ func TestEmptyResponse(t *testing.T) {
 			t.Errorf("expected /api/v1/rules response to have non-nil data")
 		}
 	})
+
+	rhWithEmptyGroup := &requestHandler{m: &manager{groups: map[uint64]*Group{0: {Name: "test"}}}}
+	ts.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { rhWithEmptyGroup.handler(w, r) })
+
+	t.Run("empty group /api/v1/rules", func(t *testing.T) {
+		lr := listGroupsResponse{}
+		getResp(ts.URL+"/api/v1/rules", &lr, 200)
+		if lr.Data.Groups == nil {
+			t.Fatalf("expected /api/v1/rules response to have non-nil data")
+		}
+
+		lr = listGroupsResponse{}
+		getResp(ts.URL+"/vmalert/api/v1/rules", &lr, 200)
+		if lr.Data.Groups == nil {
+			t.Fatalf("expected /api/v1/rules response to have non-nil data")
+		}
+
+		group := lr.Data.Groups[0]
+		if group.Rules == nil {
+			t.Fatalf("expected /api/v1/rules response to have non-nil rules for group")
+		}
+	})
 }