diff --git a/client/client.go b/client/client.go
index fb07eb42..aabbb054 100644
--- a/client/client.go
+++ b/client/client.go
@@ -763,6 +763,9 @@ func (c *QQClient) GetGroupMembers(group *GroupInfo) ([]*GroupMemberInfo, error)
 		if err != nil {
 			return nil, err
 		}
+		if data == nil {
+			return nil, errors.New("rsp is nil")
+		}
 		rsp := data.(groupMemberListResponse)
 		nextUin = rsp.NextUin
 		for _, m := range rsp.list {
@@ -829,24 +832,6 @@ func (c *QQClient) SolveFriendRequest(req *NewFriendRequest, accept bool) {
 	_ = c.send(pkt)
 }
 
-func (g *GroupInfo) SelfPermission() MemberPermission {
-	return g.FindMember(g.client.Uin).Permission
-}
-
-func (g *GroupInfo) AdministratorOrOwner() bool {
-	return g.SelfPermission() == Administrator || g.SelfPermission() == Owner
-}
-
-func (g *GroupInfo) FindMember(uin int64) *GroupMemberInfo {
-	for _, m := range g.Members {
-		f := m
-		if f.Uin == uin {
-			return f
-		}
-	}
-	return nil
-}
-
 func (c *QQClient) getCookies() string {
 	return fmt.Sprintf("uin=o%d; skey=%s;", c.Uin, c.sigInfo.sKey)
 }
@@ -914,14 +899,14 @@ func (c *QQClient) kickGroupMember(groupCode, memberUin int64, msg string) {
 }
 
 func (g *GroupInfo) removeMember(uin int64) {
-	g.memLock.Lock()
-	defer g.memLock.Unlock()
-	for i, m := range g.Members {
-		if m.Uin == uin {
-			g.Members = append(g.Members[:i], g.Members[i+1:]...)
-			break
+	g.Update(func(info *GroupInfo) {
+		for i, m := range info.Members {
+			if m.Uin == uin {
+				info.Members = append(info.Members[:i], info.Members[i+1:]...)
+				break
+			}
 		}
-	}
+	})
 }
 
 func (c *QQClient) connect() error {
@@ -1066,7 +1051,7 @@ func (c *QQClient) netLoop() {
 		go func() {
 			defer func() {
 				if pan := recover(); pan != nil {
-					c.Error("panic on decoder: %v", pan)
+					c.Error("panic on decoder %v : %v", pkt.CommandName, pan)
 					//fmt.Println("panic on decoder:", pan)
 				}
 			}()
diff --git a/client/decoders.go b/client/decoders.go
index 963af379..70e2154f 100644
--- a/client/decoders.go
+++ b/client/decoders.go
@@ -29,8 +29,8 @@ import (
 )
 
 var (
-	groupJoinLock  = new(sync.Mutex)
-	groupLeaveLock = new(sync.Mutex)
+	groupJoinLock  sync.Mutex
+	groupLeaveLock sync.Mutex
 )
 
 // wtlogin.login
@@ -228,7 +228,9 @@ func decodeMessageSvcPacket(c *QQClient, _ uint16, payload []byte) (interface{},
 							Permission: Member,
 							Group:      group,
 						}
-						group.Members = append(group.Members, mem)
+						group.Update(func(info *GroupInfo) {
+							info.Members = append(info.Members, mem)
+						})
 						c.dispatchNewMemberEvent(&MemberJoinGroupEvent{
 							Group:  group,
 							Member: mem,
@@ -459,6 +461,7 @@ func decodeGroupInfoResponse(c *QQClient, _ uint16, payload []byte) (interface{}
 		OwnerUin:       int64(*info.GroupInfo.GroupOwner),
 		MemberCount:    uint16(*info.GroupInfo.GroupMemberNum),
 		MaxMemberCount: uint16(*info.GroupInfo.GroupMemberMaxNum),
+		Members:        []*GroupMemberInfo{},
 		client:         c,
 	}, nil
 }
diff --git a/client/entities.go b/client/entities.go
index b4333066..ddbad763 100644
--- a/client/entities.go
+++ b/client/entities.go
@@ -70,8 +70,8 @@ type (
 		MaxMemberCount uint16
 		Members        []*GroupMemberInfo
 
-		client  *QQClient
-		memLock sync.Mutex
+		client *QQClient
+		lock   sync.RWMutex
 	}
 
 	GroupMemberInfo struct {
@@ -285,6 +285,42 @@ func (g *GroupInfo) Quit() {
 	}
 }
 
+func (g *GroupInfo) SelfPermission() MemberPermission {
+	return g.FindMember(g.client.Uin).Permission
+}
+
+func (g *GroupInfo) AdministratorOrOwner() bool {
+	return g.SelfPermission() == Administrator || g.SelfPermission() == Owner
+}
+
+func (g *GroupInfo) FindMember(uin int64) *GroupMemberInfo {
+	r := g.Read(func(info *GroupInfo) interface{} {
+		for _, m := range info.Members {
+			f := m
+			if f.Uin == uin {
+				return f
+			}
+		}
+		return nil
+	})
+	if r == nil {
+		return nil
+	}
+	return r.(*GroupMemberInfo)
+}
+
+func (g *GroupInfo) Update(f func(*GroupInfo)) {
+	g.lock.Lock()
+	defer g.lock.Unlock()
+	f(g)
+}
+
+func (g *GroupInfo) Read(f func(*GroupInfo) interface{}) interface{} {
+	g.lock.RLock()
+	defer g.lock.RUnlock()
+	return f(g)
+}
+
 func (m *GroupMemberInfo) DisplayName() string {
 	if m.CardName == "" {
 		return m.Nickname
diff --git a/client/global.go b/client/global.go
index b5cf93a2..c474d90e 100644
--- a/client/global.go
+++ b/client/global.go
@@ -304,8 +304,8 @@ func (c *QQClient) parseGroupMessage(m *msg.Message) *message.GroupMessage {
 			if info == nil {
 				return nil
 			}
-			group.Members = append(group.Members, mem)
 			mem = info
+			group.Members = append(group.Members, mem)
 			go c.dispatchNewMemberEvent(&MemberJoinGroupEvent{
 				Group:  group,
 				Member: info,
diff --git a/message/message.go b/message/message.go
index e4f2ed1e..a4eb863d 100644
--- a/message/message.go
+++ b/message/message.go
@@ -294,15 +294,15 @@ func ToProtoElems(elems []IMessageElement, generalFlags bool) (r []*msg.Elem) {
 				CustomFace: &msg.CustomFace{
 					FilePath: e.Filename,
 					Md5:      e.Md5,
-					Size:     e.Size,
-					Flag:     make([]byte, 4),
-					OldData:  imgOld,
+					//Size:     e.Size,
+					Flag:    make([]byte, 4),
+					OldData: imgOld,
 				},
 			})
 		case *GroupImageElement:
 			r = append(r, &msg.Elem{
 				CustomFace: &msg.CustomFace{
-					FileType: 66,
+					//FileType: 66,
 					Useful:   1,
 					Origin:   1,
 					FileId:   int32(e.FileId),