diff --git a/etcdserver/cluster.go b/etcdserver/cluster.go
index a176c4d8f..15d57de9a 100644
--- a/etcdserver/cluster.go
+++ b/etcdserver/cluster.go
@@ -27,6 +27,7 @@ import (
 	"reflect"
 	"sort"
 	"strings"
+	"sync"
 
 	etcdErr "github.com/coreos/etcd/error"
 	"github.com/coreos/etcd/pkg/flags"
@@ -58,6 +59,7 @@ type Cluster struct {
 	// removed id cannot be reused.
 	removed map[types.ID]bool
 	store   store.Store
+	sync.Mutex
 }
 
 // NewClusterFromString returns Cluster through given cluster token and parsing
@@ -112,9 +114,11 @@ func newCluster(token string) *Cluster {
 	}
 }
 
-func (c Cluster) ID() types.ID { return c.id }
+func (c *Cluster) ID() types.ID { return c.id }
 
-func (c Cluster) Members() []*Member {
+func (c *Cluster) Members() []*Member {
+	c.Lock()
+	defer c.Unlock()
 	var sms SortableMemberSlice
 	for _, m := range c.members {
 		sms = append(sms, m)
@@ -130,12 +134,16 @@ func (s SortableMemberSlice) Less(i, j int) bool { return s[i].ID < s[j].ID }
 func (s SortableMemberSlice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 
 func (c *Cluster) Member(id types.ID) *Member {
+	c.Lock()
+	defer c.Unlock()
 	return c.members[id]
 }
 
 // MemberByName returns a Member with the given name if exists.
 // If more than one member has the given name, it will panic.
 func (c *Cluster) MemberByName(name string) *Member {
+	c.Lock()
+	defer c.Unlock()
 	var memb *Member
 	for _, m := range c.members {
 		if m.Name == name {
@@ -148,7 +156,9 @@ func (c *Cluster) MemberByName(name string) *Member {
 	return memb
 }
 
-func (c Cluster) MemberIDs() []types.ID {
+func (c *Cluster) MemberIDs() []types.ID {
+	c.Lock()
+	defer c.Unlock()
 	var ids []types.ID
 	for _, m := range c.members {
 		ids = append(ids, m.ID)
@@ -158,13 +168,17 @@ func (c Cluster) MemberIDs() []types.ID {
 }
 
 func (c *Cluster) IsIDRemoved(id types.ID) bool {
+	c.Lock()
+	defer c.Unlock()
 	return c.removed[id]
 }
 
 // PeerURLs returns a list of all peer addresses. Each address is prefixed
 // with the scheme (currently "http://"). The returned list is sorted in
 // ascending lexicographical order.
-func (c Cluster) PeerURLs() []string {
+func (c *Cluster) PeerURLs() []string {
+	c.Lock()
+	defer c.Unlock()
 	endpoints := make([]string, 0)
 	for _, p := range c.members {
 		for _, addr := range p.PeerURLs {
@@ -178,7 +192,9 @@ func (c Cluster) PeerURLs() []string {
 // ClientURLs returns a list of all client addresses. Each address is prefixed
 // with the scheme (currently "http://"). The returned list is sorted in
 // ascending lexicographical order.
-func (c Cluster) ClientURLs() []string {
+func (c *Cluster) ClientURLs() []string {
+	c.Lock()
+	defer c.Unlock()
 	urls := make([]string, 0)
 	for _, p := range c.members {
 		for _, url := range p.ClientURLs {
@@ -189,7 +205,9 @@ func (c Cluster) ClientURLs() []string {
 	return urls
 }
 
-func (c Cluster) String() string {
+func (c *Cluster) String() string {
+	c.Lock()
+	defer c.Unlock()
 	sl := []string{}
 	for _, m := range c.members {
 		for _, u := range m.PeerURLs {
@@ -279,6 +297,8 @@ func (c *Cluster) ValidateConfigurationChange(cc raftpb.ConfChange) error {
 // AddMember puts a new Member into the store.
 // A Member with a matching id must not exist.
 func (c *Cluster) AddMember(m *Member) {
+	c.Lock()
+	defer c.Unlock()
 	b, err := json.Marshal(m.RaftAttributes)
 	if err != nil {
 		log.Panicf("marshal raftAttributes should never fail: %v", err)
@@ -301,6 +321,8 @@ func (c *Cluster) AddMember(m *Member) {
 // RemoveMember removes a member from the store.
 // The given id MUST exist, or the function panics.
 func (c *Cluster) RemoveMember(id types.ID) {
+	c.Lock()
+	defer c.Unlock()
 	if _, err := c.store.Delete(memberStoreKey(id), true, true); err != nil {
 		log.Panicf("delete member should never fail: %v", err)
 	}
diff --git a/etcdserver/server_test.go b/etcdserver/server_test.go
index b5a9486fc..b52e8cf8c 100644
--- a/etcdserver/server_test.go
+++ b/etcdserver/server_test.go
@@ -1382,31 +1382,6 @@ func (w *waitWithResponse) Register(id uint64) <-chan interface{} {
 }
 func (w *waitWithResponse) Trigger(id uint64, x interface{}) {}
 
-type clusterStoreRecorder struct {
-	recorder
-}
-
-func (cs *clusterStoreRecorder) Add(m Member) {
-	cs.record(action{name: "Add", params: []interface{}{m}})
-}
-func (cs *clusterStoreRecorder) Get() Cluster {
-	cs.record(action{name: "Get"})
-	return Cluster{}
-}
-func (cs *clusterStoreRecorder) Remove(id uint64) {
-	cs.record(action{name: "Remove", params: []interface{}{id}})
-}
-func (cs *clusterStoreRecorder) IsRemoved(id uint64) bool { return false }
-
-type removedClusterStore struct {
-	removed map[uint64]bool
-}
-
-func (cs *removedClusterStore) Add(m Member)             {}
-func (cs *removedClusterStore) Get() Cluster             { return Cluster{} }
-func (cs *removedClusterStore) Remove(id uint64)         {}
-func (cs *removedClusterStore) IsRemoved(id uint64) bool { return cs.removed[id] }
-
 type nopSender struct{}
 
 func (s *nopSender) Send(m []raftpb.Message) {}