diff --git a/weed/filer/filer.go b/weed/filer/filer.go
index 993175112..fe5fe289a 100644
--- a/weed/filer/filer.go
+++ b/weed/filer/filer.go
@@ -96,7 +96,7 @@ func (f *Filer) MaybeBootstrapFromPeers(self pb.ServerAddress, existingNodes []*
 func (f *Filer) AggregateFromPeers(self pb.ServerAddress, existingNodes []*master_pb.ClusterNodeUpdate, startFrom time.Time) {
 
 	f.MetaAggregator = NewMetaAggregator(f, self, f.GrpcDialOption)
-	f.MasterClient.OnPeerUpdate = f.MetaAggregator.OnPeerUpdate
+	f.MasterClient.SetOnPeerUpdateFn(f.MetaAggregator.OnPeerUpdate)
 
 	for _, peerUpdate := range existingNodes {
 		f.MetaAggregator.OnPeerUpdate(peerUpdate, startFrom)
diff --git a/weed/mq/broker/broker_server.go b/weed/mq/broker/broker_server.go
index 89afb6e4d..4c86d813f 100644
--- a/weed/mq/broker/broker_server.go
+++ b/weed/mq/broker/broker_server.go
@@ -42,7 +42,7 @@ func NewMessageBroker(option *MessageQueueBrokerOption, grpcDialOption grpc.Dial
 		MasterClient:   wdclient.NewMasterClient(grpcDialOption, option.FilerGroup, cluster.BrokerType, pb.NewServerAddress(option.Ip, option.Port, 0), option.DataCenter, option.Rack, option.Masters),
 		filers:         make(map[pb.ServerAddress]struct{}),
 	}
-	mqBroker.MasterClient.OnPeerUpdate = mqBroker.OnBrokerUpdate
+	mqBroker.MasterClient.SetOnPeerUpdateFn(mqBroker.OnBrokerUpdate)
 
 	go mqBroker.MasterClient.KeepConnectedToMaster()
 
diff --git a/weed/server/master_server.go b/weed/server/master_server.go
index ecbfd64af..758f212ad 100644
--- a/weed/server/master_server.go
+++ b/weed/server/master_server.go
@@ -116,7 +116,7 @@ func NewMasterServer(r *mux.Router, option *MasterOption, peers map[string]pb.Se
 	}
 	ms.boundedLeaderChan = make(chan int, 16)
 
-	ms.MasterClient.OnPeerUpdate = ms.OnPeerUpdate
+	ms.MasterClient.SetOnPeerUpdateFn(ms.OnPeerUpdate)
 
 	seq := ms.createSequencer(option)
 	if nil == seq {
diff --git a/weed/wdclient/masterclient.go b/weed/wdclient/masterclient.go
index 2583bda80..6e91c31eb 100644
--- a/weed/wdclient/masterclient.go
+++ b/weed/wdclient/masterclient.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"math/rand"
+	"sync"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/stats"
@@ -28,7 +29,8 @@ type MasterClient struct {
 	vidMap
 	vidMapCacheSize int
 
-	OnPeerUpdate func(update *master_pb.ClusterNodeUpdate, startFrom time.Time)
+	OnPeerUpdate           func(update *master_pb.ClusterNodeUpdate, startFrom time.Time)
+	OnPeerUpdateAccessLock sync.RWMutex
 }
 
 func NewMasterClient(grpcDialOption grpc.DialOption, filerGroup string, clientType string, clientHost pb.ServerAddress, clientDataCenter string, rack string, masters map[string]pb.ServerAddress) *MasterClient {
@@ -44,6 +46,12 @@ func NewMasterClient(grpcDialOption grpc.DialOption, filerGroup string, clientTy
 	}
 }
 
+func (mc *MasterClient) SetOnPeerUpdateFn(onPeerUpdate func(update *master_pb.ClusterNodeUpdate, startFrom time.Time)) {
+	mc.OnPeerUpdateAccessLock.Lock()
+	mc.OnPeerUpdate = onPeerUpdate
+	mc.OnPeerUpdateAccessLock.Unlock()
+}
+
 func (mc *MasterClient) GetLookupFileIdFunction() LookupFileIdFunctionType {
 	return mc.LookupFileIdWithFallback
 }
@@ -219,6 +227,7 @@ func (mc *MasterClient) tryConnectToMaster(master pb.ServerAddress) (nextHintedL
 
 			if resp.ClusterNodeUpdate != nil {
 				update := resp.ClusterNodeUpdate
+				mc.OnPeerUpdateAccessLock.RLock()
 				if mc.OnPeerUpdate != nil {
 					if update.FilerGroup == mc.FilerGroup {
 						if update.IsAdd {
@@ -230,6 +239,7 @@ func (mc *MasterClient) tryConnectToMaster(master pb.ServerAddress) (nextHintedL
 						mc.OnPeerUpdate(update, time.Now())
 					}
 				}
+				mc.OnPeerUpdateAccessLock.RUnlock()
 			}
 		}
 	})