diff --git a/client/c2c_processor.go b/client/c2c_processor.go
index f353e2e0..f71d2b71 100644
--- a/client/c2c_processor.go
+++ b/client/c2c_processor.go
@@ -117,6 +117,20 @@ func privateMessageDecoder(c *QQClient, pMsg *msg.Message, _ *network.IncomingPa
 		if pMsg.Body.RichText == nil || pMsg.Body.RichText.Elems == nil {
 			return
 		}
+
+		// handle fragmented message
+		if pMsg.Content != nil && pMsg.Content.GetPkgNum() > 1 {
+			seq := pMsg.Content.GetDivSeq()
+			builder := c.messageBuilder(seq)
+			builder.append(pMsg)
+			if builder.len() < pMsg.Content.GetPkgNum() {
+				// continue to receive other fragments
+				return
+			}
+			c.msgBuilders.Delete(seq)
+			pMsg = builder.build()
+		}
+
 		if pMsg.Head.GetFromUin() == c.Uin {
 			c.dispatchPrivateMessageSelf(c.parsePrivateMessage(pMsg))
 			return
diff --git a/client/client.go b/client/client.go
index 404a9d39..cebb22e1 100644
--- a/client/client.go
+++ b/client/client.go
@@ -82,14 +82,14 @@ type QQClient struct {
 	lastC2CMsgTime         int64
 	transCache             *utils.Cache
 	groupSysMsgCache       *GroupSystemMessages
-	groupMsgBuilders       sync.Map
+	msgBuilders            sync.Map
 	onlinePushCache        *utils.Cache
 	heartbeatEnabled       bool
 	requestPacketRequestID atomic.Int32
 	groupSeq               atomic.Int32
 	friendSeq              atomic.Int32
 	highwayApplyUpSeq      atomic.Int32
-	eventHandlers          *eventHandlers
+	eventHandlers          eventHandlers
 
 	groupListLock sync.Mutex
 }
@@ -165,7 +165,6 @@ func NewClientMd5(uin int64, passwordMd5 [16]byte) *QQClient {
 		sig: &auth.SigInfo{
 			OutPacketSessionID: []byte{0x02, 0xB0, 0x5B, 0x8B},
 		},
-		eventHandlers:   &eventHandlers{},
 		msgSvcCache:     utils.NewCache(time.Second * 15),
 		transCache:      utils.NewCache(time.Second * 15),
 		onlinePushCache: utils.NewCache(time.Second * 15),
diff --git a/client/global.go b/client/global.go
index 270af0ee..6c237e38 100644
--- a/client/global.go
+++ b/client/global.go
@@ -9,6 +9,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/pkg/errors"
@@ -26,10 +27,6 @@ import (
 type (
 	DeviceInfo = auth.Device
 	Version    = auth.OSVersion
-
-	groupMessageBuilder struct {
-		MessageSlices []*msg.Message
-	}
 )
 
 var SystemDeviceInfo = &DeviceInfo{
@@ -246,12 +243,43 @@ func (c *QQClient) parseTempMessage(msg *msg.Message) *message.TempMessage {
 	}
 }
 
-func (b *groupMessageBuilder) build() *msg.Message {
-	sort.Slice(b.MessageSlices, func(i, j int) bool {
-		return b.MessageSlices[i].Content.GetPkgIndex() < b.MessageSlices[j].Content.GetPkgIndex()
+func (c *QQClient) messageBuilder(seq int32) *messageBuilder {
+	builder := &messageBuilder{}
+	actual, ok := c.msgBuilders.LoadOrStore(seq, builder)
+	if !ok {
+		time.AfterFunc(time.Minute, func() {
+			c.msgBuilders.Delete(seq) // delete avoid memory leak
+		})
+	}
+	return actual.(*messageBuilder)
+}
+
+type messageBuilder struct {
+	lock   sync.Mutex
+	slices []*msg.Message
+}
+
+func (b *messageBuilder) append(msg *msg.Message) {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+	b.slices = append(b.slices, msg)
+}
+
+func (b *messageBuilder) len() int32 {
+	b.lock.Lock()
+	x := len(b.slices)
+	b.lock.Unlock()
+	return int32(x)
+}
+
+func (b *messageBuilder) build() *msg.Message {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+	sort.Slice(b.slices, func(i, j int) bool {
+		return b.slices[i].Content.GetPkgIndex() < b.slices[j].Content.GetPkgIndex()
 	})
-	base := b.MessageSlices[0]
-	for _, m := range b.MessageSlices[1:] {
+	base := b.slices[0]
+	for _, m := range b.slices[1:] {
 		base.Body.RichText.Elems = append(base.Body.RichText.Elems, m.Body.RichText.Elems...)
 	}
 	return base
diff --git a/client/group_msg.go b/client/group_msg.go
index 95e2e0d7..c6478888 100644
--- a/client/group_msg.go
+++ b/client/group_msg.go
@@ -311,17 +311,11 @@ func decodeGroupMessagePacket(c *QQClient, _ *network.IncomingPacketInfo, payloa
 		})
 	}
 	if pkt.Message.Content != nil && pkt.Message.Content.GetPkgNum() > 1 {
-		var builder *groupMessageBuilder
-		i, ok := c.groupMsgBuilders.Load(pkt.Message.Content.GetDivSeq())
-		if !ok {
-			builder = &groupMessageBuilder{}
-			c.groupMsgBuilders.Store(pkt.Message.Content.GetDivSeq(), builder)
-		} else {
-			builder = i.(*groupMessageBuilder)
-		}
-		builder.MessageSlices = append(builder.MessageSlices, pkt.Message)
-		if int32(len(builder.MessageSlices)) >= pkt.Message.Content.GetPkgNum() {
-			c.groupMsgBuilders.Delete(pkt.Message.Content.GetDivSeq())
+		seq := pkt.Message.Content.GetDivSeq()
+		builder := c.messageBuilder(pkt.Message.Content.GetDivSeq())
+		builder.append(pkt.Message)
+		if builder.len() >= pkt.Message.Content.GetPkgNum() {
+			c.msgBuilders.Delete(seq)
 			if pkt.Message.Head.GetFromUin() == c.Uin {
 				c.dispatchGroupMessageSelf(c.parseGroupMessage(builder.build()))
 			} else {
@@ -371,7 +365,7 @@ func decodeGetGroupMsgResponse(c *QQClient, info *network.IncomingPacketInfo, pa
 			if m.Content.GetPkgIndex() == 0 {
 				c.Debug("build fragmented message from history")
 				i := m.Head.GetMsgSeq() - m.Content.GetPkgNum()
-				builder := &groupMessageBuilder{}
+				builder := &messageBuilder{}
 				for {
 					end := int32(math.Min(float64(i+19), float64(m.Head.GetMsgSeq()+m.Content.GetPkgNum())))
 					seq, pkt := c.buildGetGroupMsgRequest(m.Head.GroupInfo.GetGroupCode(), int64(i), int64(end))
@@ -381,7 +375,7 @@ func decodeGetGroupMsgResponse(c *QQClient, info *network.IncomingPacketInfo, pa
 					}
 					for _, fm := range data.([]*message.GroupMessage) {
 						if fm.OriginalObject.Content != nil && fm.OriginalObject.Content.GetDivSeq() == m.Content.GetDivSeq() {
-							builder.MessageSlices = append(builder.MessageSlices, fm.OriginalObject)
+							builder.append(fm.OriginalObject)
 						}
 					}
 					if end >= m.Head.GetMsgSeq()+m.Content.GetPkgNum() {
diff --git a/client/image.go b/client/image.go
index bf654f58..808ae5d9 100644
--- a/client/image.go
+++ b/client/image.go
@@ -126,7 +126,7 @@ func (c *QQClient) UploadGroupImageByFile(groupCode int64, path string) (*messag
 		Ticket:    rsp.UploadKey,
 		Ext:       EmptyBytes,
 		Encrypt:   false,
-	}, 1); err == nil {
+	}, 4); err == nil {
 		goto ok
 	}
 	return nil, errors.Wrap(err, "upload failed")