diff --git a/pkg/kubernetes/kubernetes.go b/pkg/kubernetes/kubernetes.go
index 5a6620fb..081f60d2 100644
--- a/pkg/kubernetes/kubernetes.go
+++ b/pkg/kubernetes/kubernetes.go
@@ -26,6 +26,7 @@ import (
 	"io/fs"
 	"log"
 	"net/http"
+	"sort"
 	"strings"
 	"time"
 
@@ -627,6 +628,35 @@ type InstallOperatorRequest struct {
 	SubscriptionConfig     *olmv1alpha1.SubscriptionConfig
 }
 
+func mergeNamespacesEnvVar(str1, str2 string) string {
+	ns1 := strings.Split(str1, ",")
+	ns2 := strings.Split(str2, ",")
+	nsMap := map[string]struct{}{}
+
+	for _, ns := range ns1 {
+		if ns == "" {
+			continue
+		}
+		nsMap[ns] = struct{}{}
+	}
+
+	for _, ns := range ns2 {
+		if ns == "" {
+			continue
+		}
+		nsMap[ns] = struct{}{}
+	}
+
+	namespaces := []string{}
+	for ns := range nsMap {
+		namespaces = append(namespaces, ns)
+	}
+
+	sort.Strings(namespaces)
+
+	return strings.Join(namespaces, ",")
+}
+
 func mergeSubscriptionConfig(sub *olmv1alpha1.SubscriptionConfig, cfg *olmv1alpha1.SubscriptionConfig) *olmv1alpha1.SubscriptionConfig {
 	if sub == nil {
 		sub = &olmv1alpha1.SubscriptionConfig{Env: []corev1.EnvVar{}}
@@ -648,20 +678,7 @@ func mergeSubscriptionConfig(sub *olmv1alpha1.SubscriptionConfig, cfg *olmv1alph
 				}
 
 				// Merge the namespaces
-				subNamespaces := strings.Split(se.Value, ",")
-				cfgNamespaces := strings.Split(e.Value, ",")
-				namespacesMap := map[string]struct{}{}
-				for _, ns := range subNamespaces {
-					namespacesMap[ns] = struct{}{}
-				}
-				for _, ns := range cfgNamespaces {
-					namespacesMap[ns] = struct{}{}
-				}
-				namespaces := []string{}
-				for ns := range namespacesMap {
-					namespaces = append(namespaces, ns)
-				}
-				sub.Env[i].Value = strings.Join(namespaces, ",")
+				sub.Env[i].Value = mergeNamespacesEnvVar(se.Value, e.Value)
 
 				break
 			}
diff --git a/pkg/kubernetes/kubernetes_test.go b/pkg/kubernetes/kubernetes_test.go
new file mode 100644
index 00000000..7a57f15e
--- /dev/null
+++ b/pkg/kubernetes/kubernetes_test.go
@@ -0,0 +1,104 @@
+// percona-everest-cli
+// Copyright (C) 2023 Percona LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package kubernetes provides functionality for kubernetes.
+package kubernetes
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMergeNamesspacesEnvVar(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name string
+		ns1  string
+		ns2  string
+		want string
+	}{
+		{
+			name: "0-0",
+			ns1: "",
+			ns2: "",
+			want: "",
+		},
+		{
+			name: "1-0",
+			ns1: "ns1",
+			ns2: "",
+			want: "ns1",
+		},
+		{
+			name: "0-1",
+			ns1: "",
+			ns2: "ns2",
+			want: "ns2",
+		},
+		{
+			name: "1-1",
+			ns1: "ns1",
+			ns2: "ns2",
+			want: "ns1,ns2",
+		},
+		{
+			name: "1-2",
+			ns1: "ns1",
+			ns2: "ns2,ns3",
+			want: "ns1,ns2,ns3",
+		},
+		{
+			name: "1-2 unsorted",
+			ns1: "ns2",
+			ns2: "ns3,ns1",
+			want: "ns1,ns2,ns3",
+		},
+		{
+			name: "1-2 extra commas",
+			ns1: ",ns1,",
+			ns2: ",,ns2,,,,ns3,,,",
+			want: "ns1,ns2,ns3",
+		},
+		{
+			name: "2-2",
+			ns1: "ns4,ns1",
+			ns2: "ns2,ns3",
+			want: "ns1,ns2,ns3,ns4",
+		},
+		{
+			name: "0-2",
+			ns1: "",
+			ns2: "ns2,ns3",
+			want: "ns2,ns3",
+		},
+		{
+			name: "2-0 unsorted",
+			ns1: "ns4,ns1",
+			ns2: "",
+			want: "ns1,ns4",
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			mergedNS := mergeNamespacesEnvVar(tt.ns1, tt.ns2)
+			assert.Equal(t, tt.want, mergedNS)
+		})
+	}
+}
diff --git a/pkg/kubernetes/olm_operator_test.go b/pkg/kubernetes/olm_operator_test.go
index e82863d4..b4236a5a 100644
--- a/pkg/kubernetes/olm_operator_test.go
+++ b/pkg/kubernetes/olm_operator_test.go
@@ -27,6 +27,8 @@ import (
 	"go.uber.org/zap"
 	appsv1 "k8s.io/api/apps/v1"
 	corev1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 
 	"github.com/percona/percona-everest-cli/pkg/kubernetes/client"
@@ -83,11 +85,16 @@ func TestInstallOlmOperator(t *testing.T) {
 				},
 			},
 		}
+		groupResource := schema.GroupResource{
+			Group:    "operators.coreos.com",
+			Resource: "subscriptions",
+		}
+		k8sclient.On("GetSubscription", mock.Anything, subscriptionNamespace, operatorName).Return(&v1alpha1.Subscription{}, apierrors.NewNotFound(groupResource, operatorName)).Once()
 		k8sclient.On(
 			"CreateSubscription",
 			mock.Anything, subscriptionNamespace, mockSubscription,
 		).Return(mockSubscription, nil)
-		k8sclient.On("GetSubscription", mock.Anything, subscriptionNamespace, operatorName).Return(mockSubscription, nil)
+		k8sclient.On("GetSubscription", mock.Anything, subscriptionNamespace, operatorName).Return(mockSubscription, nil).Once()
 		mockInstallPlan := &v1alpha1.InstallPlan{}
 		k8sclient.On(
 			"GetInstallPlan", mock.Anything,