diff --git a/pkg/cluster/sync.go b/pkg/cluster/sync.go
index 95ce6b091..290d4ff92 100644
--- a/pkg/cluster/sync.go
+++ b/pkg/cluster/sync.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"reflect"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -425,7 +426,7 @@ func (c *Cluster) syncStatefulSet() error {
 		}
 	}
 
-	// restart instances if requiredy
+	// restart instances if required
 	remainingPods := make([]*v1.Pod, 0)
 	skipRole := Master
 	if restartMasterFirst {
@@ -572,11 +573,18 @@ func (c *Cluster) checkAndSetGlobalPostgreSQLConfiguration(pod *v1.Pod, patroniC
 		effectiveValue := effectivePgParameters[desiredOption]
 		if isBootstrapOnlyParameter(desiredOption) && (effectiveValue != desiredValue) {
 			parametersToSet[desiredOption] = desiredValue
-			if util.SliceContains(requireMasterRestartWhenDecreased, desiredOption) && (effectiveValue > desiredValue) {
-				restartMaster = append(restartMaster, true)
-			} else {
-				restartMaster = append(restartMaster, false)
+			if util.SliceContains(requireMasterRestartWhenDecreased, desiredOption) {
+				effectiveValueNum, errConv := strconv.Atoi(effectiveValue)
+				desiredValueNum, errConv2 := strconv.Atoi(desiredValue)
+				if errConv != nil || errConv2 != nil {
+					continue
+				}
+				if effectiveValueNum > desiredValueNum {
+					restartMaster = append(restartMaster, true)
+					continue
+				}
 			}
+			restartMaster = append(restartMaster, false)
 		}
 	}
 
diff --git a/pkg/cluster/sync_test.go b/pkg/cluster/sync_test.go
index e6f23914b..c6e2a8357 100644
--- a/pkg/cluster/sync_test.go
+++ b/pkg/cluster/sync_test.go
@@ -1,22 +1,40 @@
 package cluster
 
 import (
+	"bytes"
+	"io/ioutil"
+	"net/http"
 	"testing"
 	"time"
 
 	"context"
 
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/types"
 
+	"github.com/golang/mock/gomock"
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
+	"github.com/zalando/postgres-operator/mocks"
 	acidv1 "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
 	fakeacidv1 "github.com/zalando/postgres-operator/pkg/generated/clientset/versioned/fake"
 	"github.com/zalando/postgres-operator/pkg/util/config"
 	"github.com/zalando/postgres-operator/pkg/util/k8sutil"
+	"github.com/zalando/postgres-operator/pkg/util/patroni"
 	"k8s.io/client-go/kubernetes/fake"
 )
 
+var patroniLogger = logrus.New().WithField("test", "patroni")
+
+func newMockPod(ip string) *v1.Pod {
+	return &v1.Pod{
+		Status: v1.PodStatus{
+			PodIP: ip,
+		},
+	}
+}
+
 func newFakeK8sSyncClient() (k8sutil.KubernetesClient, *fake.Clientset) {
 	acidClientSet := fakeacidv1.NewSimpleClientset()
 	clientSet := fake.NewSimpleClientset()
@@ -113,3 +131,134 @@ func TestSyncStatefulSetsAnnotations(t *testing.T) {
 		t.Errorf("%s: inherited annotation not found in desired statefulset: %#v", testName, desiredSts.Annotations)
 	}
 }
+
+func TestCheckAndSetGlobalPostgreSQLConfiguration(t *testing.T) {
+	testName := "test config comparison"
+	client, _ := newFakeK8sSyncClient()
+	clusterName := "acid-test-cluster"
+	namespace := "default"
+
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	pg := acidv1.Postgresql{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      clusterName,
+			Namespace: namespace,
+		},
+		Spec: acidv1.PostgresSpec{
+			Patroni: acidv1.Patroni{
+				TTL: 20,
+			},
+			PostgresqlParam: acidv1.PostgresqlParam{
+				Parameters: map[string]string{
+					"log_min_duration_statement": "200",
+					"max_connections":            "50",
+				},
+			},
+			Volume: acidv1.Volume{
+				Size: "1Gi",
+			},
+		},
+	}
+
+	var cluster = New(
+		Config{
+			OpConfig: config.Config{
+				PodManagementPolicy: "ordered_ready",
+				Resources: config.Resources{
+					ClusterLabels:         map[string]string{"application": "spilo"},
+					ClusterNameLabel:      "cluster-name",
+					DefaultCPURequest:     "300m",
+					DefaultCPULimit:       "300m",
+					DefaultMemoryRequest:  "300Mi",
+					DefaultMemoryLimit:    "300Mi",
+					PodRoleLabel:          "spilo-role",
+					ResourceCheckInterval: time.Duration(3),
+					ResourceCheckTimeout:  time.Duration(10),
+				},
+			},
+		}, client, pg, logger, eventRecorder)
+
+	// mocking a config after setConfig is called
+	configJson := `{"postgresql": {"parameters": {"log_min_duration_statement": 200, "max_connections": 50}}}, "ttl": 20}`
+	r := ioutil.NopCloser(bytes.NewReader([]byte(configJson)))
+
+	response := http.Response{
+		StatusCode: 200,
+		Body:       r,
+	}
+
+	mockClient := mocks.NewMockHTTPClient(ctrl)
+	mockClient.EXPECT().Do(gomock.Any()).Return(&response, nil).AnyTimes()
+
+	p := patroni.New(patroniLogger, mockClient)
+	cluster.patroni = p
+	mockPod := newMockPod("192.168.100.1")
+
+	// simulate existing config that differs with cluster.Spec
+	tests := []struct {
+		subtest       string
+		pod           *v1.Pod
+		patroni       acidv1.Patroni
+		pgParams      map[string]string
+		restartMaster bool
+	}{
+		{
+			subtest: "Patroni and Postgresql.Parameters differ - restart replica first",
+			pod:     mockPod,
+			patroni: acidv1.Patroni{
+				TTL: 30, // desired 20
+			},
+			pgParams: map[string]string{
+				"log_min_duration_statement": "500", // desired 200
+				"max_connections":            "100", // desired 50
+			},
+			restartMaster: false,
+		},
+		{
+			subtest: "multiple Postgresql.Parameters differ - restart replica first",
+			pod:     mockPod,
+			patroni: acidv1.Patroni{
+				TTL: 20,
+			},
+			pgParams: map[string]string{
+				"log_min_duration_statement": "500", // desired 200
+				"max_connections":            "100", // desired 50
+			},
+			restartMaster: false,
+		},
+		{
+			subtest: "desired max_connections bigger - restart replica first",
+			pod:     mockPod,
+			patroni: acidv1.Patroni{
+				TTL: 20,
+			},
+			pgParams: map[string]string{
+				"log_min_duration_statement": "200",
+				"max_connections":            "30", // desired 50
+			},
+			restartMaster: false,
+		},
+		{
+			subtest: "desired max_connections smaller - restart master first",
+			pod:     mockPod,
+			patroni: acidv1.Patroni{
+				TTL: 20,
+			},
+			pgParams: map[string]string{
+				"log_min_duration_statement": "200",
+				"max_connections":            "100", // desired 50
+			},
+			restartMaster: true,
+		},
+	}
+
+	for _, tt := range tests {
+		requireMasterRestart, err := cluster.checkAndSetGlobalPostgreSQLConfiguration(tt.pod, tt.patroni, tt.pgParams)
+		assert.NoError(t, err)
+		if requireMasterRestart != tt.restartMaster {
+			t.Errorf("%s - %s: unexpect master restart strategy, got %v, expected %v", testName, tt.subtest, requireMasterRestart, tt.restartMaster)
+		}
+	}
+}