diff --git a/api/controller/contact.go b/api/controller/contact.go
index eb54d79fe..df9660598 100644
--- a/api/controller/contact.go
+++ b/api/controller/contact.go
@@ -97,7 +97,7 @@ func UpdateContact(dataBase moira.Database, contactDTO dto.Contact, contactData
 
 // RemoveContact deletes notification contact for current user and remove contactID from all subscriptions
 func RemoveContact(database moira.Database, contactID string, userLogin string, teamID string) *api.ErrorResponse { //nolint:gocyclo
-	var subscriptionIDs []string
+	subscriptionIDs := make([]string, 0)
 	if userLogin != "" {
 		userSubscriptionIDs, err := database.GetUserSubscriptionIDs(userLogin)
 		if err != nil {
diff --git a/filter/connection/listening.go b/filter/connection/listening.go
index 19e5d5910..f9a1a37ee 100644
--- a/filter/connection/listening.go
+++ b/filter/connection/listening.go
@@ -62,7 +62,7 @@ func (listener *MetricsListener) Listen() chan []byte {
 			conn, err := listener.listener.Accept()
 			if nil != err {
 				var opErr *net.OpError
-				if ok := errors.Is(err, opErr); ok && opErr.Timeout() {
+				if ok := errors.As(err, &opErr); ok && opErr.Timeout() {
 					continue
 				}
 				listener.logger.Info().
diff --git a/index/index_test.go b/index/index_test.go
index 7d654df92..bf1fea55c 100644
--- a/index/index_test.go
+++ b/index/index_test.go
@@ -47,7 +47,7 @@ func TestGetTriggerChecksWithRetries(t *testing.T) {
 		dataBase.EXPECT().GetTriggerChecks(randomBatch).Return(nil, expectedError).Times(3)
 		actualData, actualError := index.getTriggerChecksWithRetries(randomBatch)
 		So(actualData, ShouldBeEmpty)
-		So(actualError, ShouldResemble, fmt.Errorf("cannot get trigger checks from DB after 3 tries, last error: %w", expectedError))
+		So(actualError.Error(), ShouldResemble, fmt.Sprintf("cannot get trigger checks from DB after 3 tries, last error: %v", expectedError))
 	})
 }
 
diff --git a/notifier/plotting.go b/notifier/plotting.go
index 9992898f5..d537e0ae3 100644
--- a/notifier/plotting.go
+++ b/notifier/plotting.go
@@ -169,7 +169,7 @@ func fetchAvailableSeries(metricsSource metricSource.MetricSource, target string
 		return realtimeFetchResult.GetMetricsData(), nil
 	}
 	var errFailedWithPanic local.ErrEvaluateTargetFailedWithPanic
-	if ok := errors.Is(realtimeErr, errFailedWithPanic); ok {
+	if ok := errors.As(realtimeErr, &errFailedWithPanic); ok {
 		fetchResult, err := metricsSource.Fetch(target, from, to, false)
 		if err != nil {
 			return nil, errFetchAvailableSeriesFailed{realtimeErr: errFailedWithPanic.Error(), storedErr: err.Error()}
diff --git a/notifier/plotting_test.go b/notifier/plotting_test.go
index eb5795b3b..6e0abcd14 100644
--- a/notifier/plotting_test.go
+++ b/notifier/plotting_test.go
@@ -224,7 +224,7 @@ func TestFetchAvailableSeries(t *testing.T) {
 
 		Convey("with error ErrEvaluateTargetFailedWithPanic and error again", func() {
 			var err error = local.ErrEvaluateTargetFailedWithPanic{}
-			var secondErr = errors.New("Test error")
+			var secondErr = errors.New("test error")
 			gomock.InOrder(
 				source.EXPECT().Fetch("testTarget", int64(17), int64(67), true).Return(nil, err).Times(1),
 				source.EXPECT().Fetch("testTarget", int64(17), int64(67), false).Return(nil, secondErr).Times(1),
@@ -234,7 +234,7 @@ func TestFetchAvailableSeries(t *testing.T) {
 		})
 
 		Convey("with unknown error", func() {
-			var err error = errors.New("Test error")
+			var err = errors.New("test error")
 			gomock.InOrder(
 				source.EXPECT().Fetch("testTarget", int64(17), int64(67), true).Return(nil, err).Times(1),
 			)
diff --git a/senders/telegram/send.go b/senders/telegram/send.go
index 8d50759d7..fa0e2e59a 100644
--- a/senders/telegram/send.go
+++ b/senders/telegram/send.go
@@ -2,10 +2,11 @@ package telegram
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"strings"
 
+	"errors"
+
 	"gopkg.in/tucnak/telebot.v2"
 
 	"github.com/moira-alert/moira"
@@ -147,8 +148,9 @@ func checkBrokenContactError(logger moira.Logger, err error) error {
 	if err == nil {
 		return nil
 	}
+
 	var e *telebot.APIError
-	if ok := errors.Is(err, e); ok {
+	if ok := errors.As(err, &e); ok {
 		logger.Debug().
 			Int("code", e.Code).
 			String("msg", e.Message).